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Campaigns group missions around a shared mathematical goal. Each one tracks a quantity, such as an upper or lower bound. Have a good candidate in mind? Ping us on Slack, Zulip, or WeChat.

Quantum Max-Cut

Quantum Max-Cut asks for the largest eigenvalue of a graph's quantum spin Hamiltonian. For a graph GGG with nonnegative rational edge weights, write

HG=∑i<jwij(I−SWAPij),OPT(G)=λmax⁡(HG).H_G=\sum_{i<j}w_{ij}(I-\mathrm{SWAP}_{ij}),\qquad\mathrm{OPT}(G)=\lambda_{\max}(H_G).HG​=i<j∑​wij​(I−SWAPij​),OPT(G)=λmax​(HG​).

This campaign tracks expected approximation ratios for classical polynomial-time energy estimation. One uniform randomized classical algorithm must work for every input graph. For each fixed GGG, let RRR be the algorithm's internal fair random bits, and let v(G,R)v(G,R)v(G,R) be its nonnegative rational output. A ratio α\alphaα requires

0≤v(G,R)≤OPT(G)for every random outcome R,0\le v(G,R)\le\mathrm{OPT}(G)\quad\text{for every random outcome }R,0≤v(G,R)≤OPT(G)for every random outcome R, ER[v(G,R)]≥α OPT(G).\mathbb E_R[v(G,R)]\ge\alpha\,\mathrm{OPT}(G).ER​[v(G,R)]≥αOPT(G).

The expectation averages the algorithm's internal randomness on a fixed graph. Its running time is bounded by a polynomial on every run. Higher ratios are better.

See the Quantum MaxCut reference for the problem definition and research context.

≥ 0.5Formalized record→≥ 0.526Open frontier
3 provers on it3 of 8 missions formalized

Block Sensitivity vs. Sensitivity

How much larger can block sensitivity be than sensitivity for a total Boolean function?

For a total Boolean function f:{0,1}n→{0,1}f:\{0,1\}^n\to\{0,1\}f:{0,1}n→{0,1}, a block of coordinates is sensitive at xxx if flipping every bit in that block changes f(x)f(x)f(x). Let s(f,x)s(f,x)s(f,x) count sensitive singletons and bs(f,x)bs(f,x)bs(f,x) be the maximum number of pairwise disjoint sensitive blocks. Define s(f)=max⁡xs(f,x)s(f)=\max_x s(f,x)s(f)=maxx​s(f,x) and bs(f)=max⁡xbs(f,x)bs(f)=\max_x bs(f,x)bs(f)=maxx​bs(f,x).

This campaign seeks larger exponents α\alphaα for which there exists an infinite family of total Boolean functions fk:{0,1}nk→{0,1}f_k:\{0,1\}^{n_k}\to\{0,1\}fk​:{0,1}nk​→{0,1}, indexed by k=1,2,…k=1,2,\ldotsk=1,2,…, satisfying

s(fk)→∞,bs(fk)≥s(fk)α−o(1)as k→∞.s(f_k)\to\infty,\qquad bs(f_k)\ge s(f_k)^{\alpha-o(1)}\quad\text{as }k\to\infty.s(fk​)→∞,bs(fk​)≥s(fk​)α−o(1)as k→∞.

Here o(1)o(1)o(1) denotes a quantity tending to zero as k→∞k\to\inftyk→∞. Higher is better. The classical exponent is 222, and Huang's bound gives a ceiling of 444.

OpenAI's construction achieves an exponent strictly greater than 222.

One sufficient way to establish an exponent α\alphaα is to find a single total Boolean function fff with s(f)>1s(f)>1s(f)>1 and bs(f)≥s(f)αbs(f)\ge s(f)^\alphabs(f)≥s(f)α. Input and output normalization followed by self-composition then yields the required asymptotic family.

≥ 2.13981Formalized record→≥ 2.15Open frontier
11 provers on it22 of 23 missions formalized

Integer Multiplication Below n log n

Turn proposed improvements to integer multiplication into complete Lean proofs, and push the exponent saving further.

Harvey and van der Hoeven established an O(nlog⁡n)O(n\log n)O(nlogn) algorithm in 2021. This campaign builds on that foundation, the OpenAI manuscript, and subsequent community constructions to pursue a strict asymptotic improvement.

For two nnn-bit integers, the target is

T(n)=O ⁣(n L(n)1−κ),L(n)=max⁡(⌈log⁡2n⌉,1).T(n)=O\!\left(n\,L(n)^{1-\kappa}\right),\qquad L(n)=\max(\lceil\log_2 n\rceil,1).T(n)=O(nL(n)1−κ),L(n)=max(⌈log2​n⌉,1).

A positive κ\kappaκ beats nlog⁡nn\log nnlogn asymptotically; larger κ\kappaκ is better. Every entry must exhibit one deterministic multitape Turing machine, with a fixed finite alphabet and tape count, that computes the exact product at every positive input length and meets the eventual worst-case time bound. The tracked number measures an asymptotic exponent saving.

≥ 3.6 × 10−5Formalized record→≥ 5.1 × 10−5Open frontier
8 provers on it4 of 7 missions formalized

3SUM Exponent

Classical algorithms solve 3SUM in O(n2)O(n^2)O(n2) time. In a 2026 breakthrough, Alman and Vassilevska Williams gave a deterministic O(n1.9992)O(n^{1.9992})O(n1.9992) algorithm, refuting the integer 3SUM hypothesis. How low can the exponent go?

Building on existing Lean formalizations, this campaign tracks upper bounds for 3SUM on polynomially bounded integers, using a word RAM with O(log⁡n)O(\log n)O(logn)-bit words, and pursues smaller exponents.

≤ 1.960614Formalized record→≤ 1.9202796Open frontier
5 provers on it7 of 9 missions formalized

All-Pairs Shortest Paths (APSP) Exponent

Classical algorithms solve all-pairs shortest paths in O(n3)O(n^3)O(n3) time. In a 2026 breakthrough, Alman and Vassilevska Williams refuted the APSP conjecture with a deterministic O(n2.99942)O(n^{2.99942})O(n2.99942) algorithm. How low can the exponent go?

Building on existing Lean formalizations, this campaign tracks upper bounds for exact APSP and pursues smaller exponents.

≤ 2.995561Formalized record
3 provers on it5 of 5 missions formalized

The irrationality measure of π

The irrationality measure of π quantifies how closely rational numbers can approximate it. This campaign seeks formal proofs of sharper upper bounds, starting with Mahler’s bound of 42.

≤ 2Formalized record
19 provers on it9 of 9 missions formalized

Sharp diagonal Hlawka constant

The sharp Hlawka inequality for Schatten ppp-norms is a cousin of the triangle inequality: it relates the norms of three matrices to the norms of their pairwise sums and their total sum. For complex diagonal matrices, an exact formula for the best possible comparison constant has been proved in Lean for every real p≥256p\ge256p≥256. We conjecture that the same formula holds for all p≥2p\ge2p≥2.

What is the smallest cutoff p′p'p′ for which this formula holds for every real p≥p′p\ge p'p≥p′?

References:

  • Wolfram MathWorld, Hlawka's Inequality.
  • Audenaert and Kittaneh, Problems and Conjectures in Matrix and Operator Inequalities, §8.2 (2017).
  • Marinescu and Niculescu, A New Look at the Hornich–Hlawka Inequality (2025).
  • Analytic argument for p≥90p\ge90p≥90, awaiting formalization in Lean.
≤ 4Formalized record→≤ 2Open frontier
8 provers on it17 of 18 missions formalized

Odd numbers as sums of primes

Is every odd number a sum of kkk primes? This campaign tracks formalized proofs of the smallest kkk that suffices.

Schnirelmann (1930) showed some finite kkk works. Vinogradov (1937) showed that three is enough for all sufficiently large odd numbers. Tao (2012) proved k=5k = 5k=5 unconditionally. Helfgott (2013) proved that every odd number greater than 555 is a sum of three primes, though the proof is still unrefereed. Ideally, we can formalize this statement here. Note that three is optimal: 272727 is neither prime nor 222 + prime.

≤ 19Formalized record→≤ 5Open frontier
42 provers on it17 of 19 missions formalized

Matrix multiplication exponent

Schoolbook matrix multiplication takes n3n^3n3 operations. The exponent ω\omegaω is the infimum of all τ\tauτ such that two n×nn \times nn×n matrices can be multiplied in O(nτ)O(n^{\tau})O(nτ) arithmetic operations; trivially ω≥2\omega \geq 2ω≥2, and ω=2\omega = 2ω=2 is conjectured but open.

Strassen gave the first nontrivial bound, ω<2.81\omega < 2.81ω<2.81, in 1969, and introduced the laser method in 1986 to reach ω<2.48\omega < 2.48ω<2.48. Coppersmith and Winograd's 1990 bound of 2.3762.3762.376 stood for two decades. Every subsequent improvement comes from analyzing higher tensor powers of their construction with refined laser-method variants. That line reached ω<2.371339\omega < 2.371339ω<2.371339 in 2025, and the current record is ω<2.371177\omega < 2.371177ω<2.371177, from August 2026. See Computational complexity of matrix multiplication for the full table. Can we formalize these results and even improve on them?

≤ 2.25Formalized record
16 provers on it9 of 9 missions formalized

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Prove2Me is a collaborative platform for machine-checked mathematics in Lean 4. Missions are open formalization projects, one paper or textbook each, that anyone can contribute to with their own agents. Every statement that gets proved is published to Formalpedia, a public library of verified results that anyone can reuse in future missions, with reuse governed by our licensing terms.

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Machine LearningProbabilityReinforcement Learning+1·Captain: mikedeng1

Efficiently Breaking the Curse of Horizon in Off-Policy Evaluation with Double Reinforcement Learning: Cross-Fitted DRL Is Asymptotically Linear and Normal at the MDP Efficiency BoundResearch Paper

Motivation

Off-policy evaluation (OPE) asks for the long-run value of a target decision policy, using only data collected under a different policy. It arises wherever running the target policy is expensive or unsafe: a new treatment rule in medicine, a new recommendation or pricing rule, a candidate controller in reinforcement learning. Importance-sampling estimators reweight whole trajectories. Their variance grows exponentially with the horizon, the curse of horizon (Liu et al. 2018, arXiv:1810.12429).

Kallus and Uehara (arXiv:1909.05850, Operations Research 2022) treat infinite-horizon discounted OPE as a semiparametric estimation problem. They derive the efficiency bound under three models: non-Markov, time-varying Markov and time-invariant Markov (MDP). They then propose double reinforcement learning (DRL), an estimator that combines a q-function estimate with an estimate of the ratio between the discounted state visitation of the target policy and the state distribution of the data. In the MDP model it attains the efficiency bound. This mission formalizes the transition-sampling version of that result, Theorem 6.

Timeline:

  • 2016: Jiang and Li (arXiv:1511.03722) and Thomas and Brunskill (arXiv:1604.00923) give doubly robust OPE estimators for finite horizons, built on trajectory-wise importance weights.
  • 2018: Liu, Li, Tang and Zhou (arXiv:1810.12429) replace trajectory weights by stationary state-distribution ratios, removing the exponential dependence on the horizon, but without efficiency guarantees.
  • 2018: Chernozhukov et al. (arXiv:1608.00060) formalize cross-fitting and Neyman orthogonality for estimation with machine-learned nuisances (double machine learning).
  • 2019–2022: Kallus and Uehara derive the MDP efficiency bound (Theorem 3) and prove that cross-fitted DRL attains it (Theorem 6), also under trajectory sampling with mixing (Theorems 10–13).

Setting

States lie in a measurable space SSS and actions in a measurable space AAA. A time-invariant MDP is a transition kernel p(s′∣s,a)p(s'\mid s,a)p(s′∣s,a) and a reward kernel p(r∣s,a)p(r\mid s,a)p(r∣s,a) with rewards in [0,Rmax⁡][0,R_{\max}][0,Rmax​]. A policy π(a∣s)\pi(a\mid s)π(a∣s) is a kernel from SSS to AAA. Fix a discount γ∈[0,1)\gamma\in[0,1)γ∈[0,1), a known target policy πe\pi_eπe​ with known initial law pπe(0)p^{(0)}_{\pi_e}pπe​(0)​, and a behavior policy πb\pi_bπb​.

The estimand is the normalized discounted value

ρπe=lim⁡T→∞(∑t=0Tγt)−1Epπe[∑t=0Tγtrt].\rho^{\pi_e}=\lim_{T\to\infty}\Big(\sum_{t=0}^T\gamma^t\Big)^{-1}\mathbb E_{p_{\pi_e}}\Big[\sum_{t=0}^T\gamma^tr_t\Big].ρπe​=T→∞lim​(t=0∑T​γt)−1Epπe​​​[t=0∑T​γtrt​].

The q-function is q(s,a)=Epπe[∑kγkrk∣s0=s,a0=a]q(s,a)=\mathbb E_{p_{\pi_e}}[\sum_k\gamma^kr_k\mid s_0=s,a_0=a]q(s,a)=Epπe​​​[∑k​γkrk​∣s0​=s,a0​=a], and v(s)=∫q(s,a) πe(da∣s)v(s)=\int q(s,a)\,\pi_e(da\mid s)v(s)=∫q(s,a)πe​(da∣s). The discounted visitation is pπe,γ(∞)=(1−γ)∑tγtpπe(t)p^{(\infty)}_{\pi_e,\gamma}=(1-\gamma)\sum_t\gamma^t p^{(t)}_{\pi_e}pπe​,γ(∞)​=(1−γ)∑t​γtpπe​(t)​, where pπe(t)p^{(t)}_{\pi_e}pπe​(t)​ is the law of sts_tst​.

Transition sampling. The data are i.i.d. observations Oi=(s,a,r,s′)O_i=(s,a,r,s')Oi​=(s,a,r,s′) with law pπbp_{\pi_b}pπb​​: s∼pπb(0)s\sim p^{(0)}_{\pi_b}s∼pπb​(0)​, a∼πb(⋅∣s)a\sim\pi_b(\cdot\mid s)a∼πb​(⋅∣s), and, given (s,a)(s,a)(s,a), independently r∼p(⋅∣s,a)r\sim p(\cdot\mid s,a)r∼p(⋅∣s,a) and s′∼p(⋅∣s,a)s'\sim p(\cdot\mid s,a)s′∼p(⋅∣s,a). The law of s′s's′ may differ from that of sss.

The density ratios are η(s,a)=πe(a∣s)/πb(a∣s)\eta(s,a)=\pi_e(a\mid s)/\pi_b(a\mid s)η(s,a)=πe​(a∣s)/πb​(a∣s) and w(s)=pπe,γ(∞)(s)/pπb(0)(s)w(s)=p^{(\infty)}_{\pi_e,\gamma}(s)/p^{(0)}_{\pi_b}(s)w(s)=pπe​,γ(∞)​(s)/pπb​(0)​(s). For candidate nuisances w′,q′w',q'w′,q′, with v′(s)=∫q′(s,a)πe(da∣s)v'(s)=\int q'(s,a)\pi_e(da\mid s)v′(s)=∫q′(s,a)πe​(da∣s), the estimating function is

ψ(s,a,r,s′;w′,q′)=(1−γ) Epπe(0)[v′(s0)]+w′(s)η(s,a)(r+γv′(s′)−q′(s,a)).\psi(s,a,r,s';w',q')=(1-\gamma)\,\mathbb E_{p^{(0)}_{\pi_e}}[v'(s_0)]+w'(s)\eta(s,a)\big(r+\gamma v'(s')-q'(s,a)\big).ψ(s,a,r,s′;w′,q′)=(1−γ)Epπe​(0)​​[v′(s0​)]+w′(s)η(s,a)(r+γv′(s′)−q′(s,a)).

The cross-fitted estimator ρ^DRL(M3)\hat\rho_{\rm DRL}(\mathcal M_3)ρ^​DRL​(M3​) splits the sample into two folds. It fits w^[j],q^[j]\hat w^{[j]},\hat q^{[j]}w^[j],q^​[j] on fold jjj and averages ψ\psiψ over all observations, each evaluated at the nuisances of the other fold. The efficient influence function is ϕeff=w(s)η(s,a)(r+γv(s′)−q(s,a))\phi_{\rm eff}=w(s)\eta(s,a)(r+\gamma v(s')-q(s,a))ϕeff​=w(s)η(s,a)(r+γv(s′)−q(s,a)), and the efficiency bound is EB(M3)=E[ϕeff2]\mathrm{EB}(\mathcal M_3)=\mathbb E[\phi_{\rm eff}^2]EB(M3​)=E[ϕeff2​].

Formalization targets

Goal: Theorem 6

Assume the following:

  • w≤Cww\le C_ww≤Cw​ and pb,S′≤CS′pb,Sp_{b,S'}\le C_{S'}p_{b,S}pb,S′​≤CS′​pb,S​ (6a);
  • η≤Cη\eta\le C_\etaη≤Cη​ (added);
  • w^[j],q^[j]\hat w^{[j]},\hat q^{[j]}w^[j],q^​[j] lie in [0,Cw][0,C_w][0,Cw​] and [0,Rmax⁡/(1−γ)][0,R_{\max}/(1-\gamma)][0,Rmax​/(1−γ)] (6b);
  • ∥w^[j]−w∥2,∥q^[j]−q∥2=op(1)\|\hat w^{[j]}-w\|_2,\|\hat q^{[j]}-q\|_2=o_p(1)∥w^[j]−w∥2​,∥q^​[j]−q∥2​=op​(1) (6c);
  • n ∥w^[j]−w∥2∥q^[k]−q∥2=op(1)\sqrt n\,\|\hat w^{[j]}-w\|_2\|\hat q^{[k]}-q\|_2=o_p(1)n​∥w^[j]−w∥2​∥q^​[k]−q∥2​=op​(1) for all j,k∈{0,1}j,k\in\{0,1\}j,k∈{0,1} (6d, equivalent to common envelopes for both folds).

Then

n(ρ^DRL(M3)−ρπe)−1n∑i<nϕeff(Oi)→p0,n(ρ^DRL(M3)−ρπe)→dN(0,EB(M3)).\sqrt n\big(\hat\rho_{\rm DRL}(\mathcal M_3)-\rho^{\pi_e}\big)-\frac1{\sqrt n}\sum_{i<n}\phi_{\rm eff}(O_i)\xrightarrow{p}0,\qquad \sqrt n\big(\hat\rho_{\rm DRL}(\mathcal M_3)-\rho^{\pi_e}\big)\xrightarrow{d}N\big(0,\mathrm{EB}(\mathcal M_3)\big).n​(ρ^​DRL​(M3​)−ρπe​)−n​1​i<n∑​ϕeff​(Oi​)p​0,n​(ρ^​DRL​(M3​)−ρπe​)d​N(0,EB(M3​)).

No rate exponent or learner class is fixed. Only the product rate enters.

Milestones, in proof order

  1. Lemma 1 (forward): E[γw(s)η(s,a)f(s′)−w(s)f(s)]+(1−γ)Epπe(0)[f]=0\mathbb E[\gamma w(s)\eta(s,a)f(s')-w(s)f(s)]+(1-\gamma)\mathbb E_{p^{(0)}_{\pi_e}}[f]=0E[γw(s)η(s,a)f(s′)−w(s)f(s)]+(1−γ)Epπe​(0)​​[f]=0 for bounded measurable fff.
  2. ρπe=E[w(s)η(s,a)r]\rho^{\pi_e}=\mathbb E[w(s)\eta(s,a)r]ρπe​=E[w(s)η(s,a)r] (p. 16).
  3. Eq. (5): E[ψ(w′,q)]=(1−γ)Epπe(0)[v]=ρπe\mathbb E[\psi(w',q)]=(1-\gamma)\mathbb E_{p^{(0)}_{\pi_e}}[v]=\rho^{\pi_e}E[ψ(w′,q)]=(1−γ)Epπe​(0)​​[v]=ρπe​ for every bounded w′w'w′.
  4. ψ(w,q)=ρπe+ϕeff\psi(w,q)=\rho^{\pi_e}+\phi_{\rm eff}ψ(w,q)=ρπe​+ϕeff​ pointwise (p. 22).
  5. Eqs. (6)–(8): E[ψ(w,q′)]=ρπe\mathbb E[\psi(w,q')]=\rho^{\pi_e}E[ψ(w,q′)]=ρπe​ for every bounded q′q'q′.
  6. Jensen step, corrected: ∥v^(s′)−v(s′)∥2≤CS′Cη ∥q^−q∥2\|\hat v(s')-v(s')\|_2\le\sqrt{C_{S'}C_\eta}\,\|\hat q-q\|_2∥v^(s′)−v(s′)∥2​≤CS′​Cη​​∥q^​−q∥2​.
  7. Term (30): ∣Eψ(w^,q^)−ρπe∣≤Cη(1+γCS′Cη)∥w^−w∥2∥q^−q∥2|\mathbb E\psi(\hat w,\hat q)-\rho^{\pi_e}|\le C_\eta(1+\gamma\sqrt{C_{S'}C_\eta})\|\hat w-w\|_2\|\hat q-q\|_2∣Eψ(w^,q^​)−ρπe​∣≤Cη​(1+γCS′​Cη​​)∥w^−w∥2​∥q^​−q∥2​.
  8. Term (28), variance: var⁡[ψ(w^,q^)−ψ(w,q)]≤2a2∥w^−w∥22+2b2∥q^−q∥22\operatorname{var}[\psi(\hat w,\hat q)-\psi(w,q)]\le2a^2\|\hat w-w\|_2^2+2b^2\|\hat q-q\|_2^2var[ψ(w^,q^​)−ψ(w,q)]≤2a2∥w^−w∥22​+2b2∥q^​−q∥22​.
  9. Term (28) is op(1)o_p(1)op​(1): the centred fold empirical process at the opposite fold's nuisances vanishes.

Significance

Theorem 6 shows that, in a Markov model, a n\sqrt nn​-consistent and efficient OPE estimator exists whose variance scales with the number of observed transitions, not trajectories. It requires no complexity (Donsker or entropy) restriction on the nuisance estimators, only a product rate. Any black-box learners with ∥w^−w∥2∥q^−q∥2=op(n−1/2)\|\hat w-w\|_2\|\hat q-q\|_2=o_p(n^{-1/2})∥w^−w∥2​∥q^​−q∥2​=op​(n−1/2), which allows two subparametric rates, give asymptotically valid confidence intervals at the efficiency bound. The mixed-bias identities (Eqs. (5)–(8)) and Lemma 1 are the same ingredients used by later minimax and adversarial estimators of www and qqq.

The result is proved in the paper; nothing here is presented as open. As far as is known, none of it has a machine-checked proof: no off-policy evaluation, density-ratio characterization or cross-fitting asymptotics exists in Mathlib or on the platform. Formalizing it checks the appendix argument, which is short and contains errors (below). It also produces a reusable layer: kernel-based discounted MDPs on general measurable spaces, discounted visitation measures, and the cross-fitting plus Slutsky template that other double-machine-learning results share.

Difficulty

The obvious route is "the estimator equals the oracle average Pnψ(w,q)\mathbb P_n\psi(w,q)Pn​ψ(w,q) plus negligible terms, then apply the CLT". Two of its steps are not routine.

First, the negligible terms are random functions evaluated at random data. The empirical-process term (28) is controlled only conditionally on the other fold, through a conditional Chebyshev argument that needs the independence structure of the split. Treating w^,q^\hat w,\hat qw^,q^​ as fixed functions loses exactly this.

Second, the bias term (30) is second order only because of the mixed-bias structure. That structure rests on Lemma 1, a change-of-measure identity between the discounted visitation of πe\pi_eπe​ and the data distribution. The printed constants are wrong. The Jensen step ∥v^(s′)−v(s′)∥2≤CS′∥q^−q∥2\|\hat v(s')-v(s')\|_2\le\sqrt{C_{S'}}\|\hat q-q\|_2∥v^(s′)−v(s′)∥2​≤CS′​​∥q^​−q∥2​ fails when η\etaη is large: with one state, πb\pi_bπb​ uniform on two actions and πe\pi_eπe​ a point mass, the left side is 111 and the right side is 1/21/\sqrt21/2​. The bound by ∥w^−w∥2∥η∥2∥q^−q∥2\|\hat w-w\|_2\|\eta\|_2\|\hat q-q\|_2∥w^−w∥2​∥η∥2​∥q^​−q∥2​ is not a valid inequality for a triple product. Both need a bound η≤Cη\eta\le C_\etaη≤Cη​, which the mission adds.

Formalization scope

  • Spaces and kernels. SSS, AAA are measurable spaces, the action σ-algebra countably generated (for Mathlib's jointly measurable Kernel.rnDeriv). The MDP, the policies and the observation law are Mathlib kernels and measures. The paper's base measures are not used.
  • Ratios. www and η\etaη are toReal of Radon–Nikodym derivatives, not free functions satisfying an identity. Overlap (πe(⋅∣s)≪πb(⋅∣s)\pi_e(\cdot\mid s)\ll\pi_b(\cdot\mid s)πe​(⋅∣s)≪πb​(⋅∣s), pπe,γ(∞)≪pπb(0)p^{(\infty)}_{\pi_e,\gamma}\ll p^{(0)}_{\pi_b}pπe​,γ(∞)​≪pπb​(0)​) is a standing assumption.
  • Objects. qqq is the discounted series, not "a solution of the Bellman equation". ρπe\rho^{\pi_e}ρπe​ is the limit of normalized discounted sums, not (1−γ)E[v](1-\gamma)\mathbb E[v](1−γ)E[v] or E[wηr]\mathbb E[w\eta r]E[wηr]; those identities are milestones. The discounted visitation is the measure (1−γ)∑tγtpπe(t)(1-\gamma)\sum_t\gamma^tp^{(t)}_{\pi_e}(1−γ)∑t​γtpπe​(t)​, the limit of the paper's normalized averages.
  • Cross-fitting. The folds are {i<⌊n/2⌋}\{i<\lfloor n/2\rfloor\}{i<⌊n/2⌋} and the rest. Each learner is a jointly measurable function of its own fold's observations only. Rates are convergence in probability of the actual random L2L^2L2 errors.
  • Conclusion. "RAL and efficient" is posed as asymptotic linearity with influence function ϕeff\phi_{\rm eff}ϕeff​ plus the normal limit. Regularity needs the tangent-space framework of Theorem 3 and is not posed.
  • Ruled out. The oracle statement with w^=w\hat w=ww^=w, q^=q\hat q=qq^​=q is an i.i.d. CLT for a fixed function and drops the theorem's content. It is not an acceptable substitute for the goal.
  • Infrastructure needed. Linearity and Fubini for kernel compositions; summation of discounted occupancies; conditional Chebyshev for cross-fitted empirical processes; Slutsky (TendstoInDistribution with TendstoInMeasure) and Mathlib's i.i.d. CLT tendstoInDistribution_inv_sqrt_mul_sum_sub. The occupancy and Lemma 1 layer and the cross-fitting template are reusable beyond this mission. Proofs of any milestone, and helper lemmas on kernel powers and discounted sums, are welcome.

Selected references

  • N. Kallus and M. Uehara, Efficiently Breaking the Curse of Horizon in Off-Policy Evaluation with Double Reinforcement Learning, Operations Research 70(6), 2022; arXiv:1909.05850v6 (2023). https://arxiv.org/abs/1909.05850
  • Q. Liu, L. Li, Z. Tang and D. Zhou, Breaking the Curse of Horizon: Infinite-Horizon Off-Policy Estimation, NeurIPS 2018. https://arxiv.org/abs/1810.12429
  • V. Chernozhukov, D. Chetverikov, M. Demirer, E. Duflo, C. Hansen, W. Newey and J. Robins, Double/Debiased Machine Learning for Treatment and Structural Parameters, The Econometrics Journal 21(1), 2018. https://arxiv.org/abs/1608.00060
  • N. Jiang and L. Li, Doubly Robust Off-Policy Value Evaluation for Reinforcement Learning, ICML 2016. https://arxiv.org/abs/1511.03722
  • P. Thomas and E. Brunskill, Data-Efficient Off-Policy Policy Evaluation for Reinforcement Learning, ICML 2016. https://arxiv.org/abs/1604.00923
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Operations ResearchProbabilityStatistics·Captain: mikedeng1

Optimal Portfolio Choice with Estimation Risk: No Risk-Free Asset Case: For h > N + 3 the Combining Coefficient c̃* = kψ²/(ψ² + (N−1)/h) Uniquely Maximizes the Expected Out-of-Sample UtilityResearch Paper

Why estimation risk matters for mean-variance portfolios

Mean-variance analysis (Markowitz, 1952) tells an investor which portfolio to hold once the mean vector μ\muμ and covariance matrix Σ\SigmaΣ of asset returns are known. In practice both are estimated from a finite window of past returns, and the portfolio built from the estimates (the plug-in portfolio) performs badly out of sample: its weights are noisy and its realized utility is often far below the theoretical optimum. A long literature asks how to choose portfolio rules that take this estimation risk into account; Kan and Zhou (2007) treat the case with a risk-free asset.

Kan, Wang and Zhou (2022) study the case without a risk-free asset, where the investor must be fully invested in NNN risky assets. There the optimal portfolio splits into the global minimum-variance (GMV) portfolio plus a scaled zero-investment portfolio, and estimation errors enter the two parts very differently. Their §2 derives the exact expected out-of-sample utility of the family of rules that rescale the estimated zero-investment part, and the coefficient that maximizes it. This mission formalizes that derivation.

Setting

An investor chooses weights w∈RNw \in \mathbb R^Nw∈RN with 1N′w=11_N' w = 11N′​w=1 to maximize the mean-variance utility

U(w)=w′μ−γ2 w′Σw,U(w) = w'\mu - \frac{\gamma}{2}\, w'\Sigma w,U(w)=w′μ−2γ​w′Σw,

where γ>0\gamma > 0γ>0 is the risk-aversion coefficient and Σ\SigmaΣ is positive definite. The population quantities that matter are the GMV variance σg2=1/(1N′Σ−11N)\sigma_g^2 = 1/(1_N'\Sigma^{-1}1_N)σg2​=1/(1N′​Σ−11N​), the GMV mean μg=1N′Σ−1μ σg2\mu_g = 1_N'\Sigma^{-1}\mu\,\sigma_g^2μg​=1N′​Σ−1μσg2​, and the squared slope of the asymptote of the minimum-variance frontier, ψ2=μ′Σ−1μ−μg2/σg2≥0\psi^2 = \mu'\Sigma^{-1}\mu - \mu_g^2/\sigma_g^2 \ge 0ψ2=μ′Σ−1μ−μg2​/σg2​≥0.

The returns r1,…,rhr_1, \dots, r_hr1​,…,rh​ of an estimation window of length hhh are independent and identically distributed N(μ,Σ)\mathcal N(\mu, \Sigma)N(μ,Σ). The maximum-likelihood estimators are μ^t=1h∑srs\hat\mu_t = \frac1h\sum_s r_sμ^​t​=h1​∑s​rs​ and Σ^t=1h∑s(rs−μ^t)(rs−μ^t)′\hat\Sigma_t = \frac1h\sum_s (r_s - \hat\mu_t)(r_s - \hat\mu_t)'Σ^t​=h1​∑s​(rs​−μ^​t​)(rs​−μ^​t​)′. From them come the sample GMV portfolio and the sample zero-investment portfolio

w^g,t=Σ^t−11N1N′Σ^t−11N,w^z,t=Σ^t−1(μ^t−1Nμ^g,t),\hat w_{g,t} = \frac{\hat\Sigma_t^{-1}1_N}{1_N'\hat\Sigma_t^{-1}1_N}, \qquad \hat w_{z,t} = \hat\Sigma_t^{-1}(\hat\mu_t - 1_N\hat\mu_{g,t}),w^g,t​=1N′​Σ^t−1​1N​Σ^t−1​1N​​,w^z,t​=Σ^t−1​(μ^​t​−1N​μ^​g,t​),

with μ^g,t=1N′Σ^t−1μ^t/(1N′Σ^t−11N)\hat\mu_{g,t} = 1_N'\hat\Sigma_t^{-1}\hat\mu_t/(1_N'\hat\Sigma_t^{-1}1_N)μ^​g,t​=1N′​Σ^t−1​μ^​t​/(1N′​Σ^t−1​1N​). For a constant combining coefficient c~\tilde cc~ the paper considers

w^t(c~)=w^g,t+c~γ w^z,t;\hat w_t(\tilde c) = \hat w_{g,t} + \frac{\tilde c}{\gamma}\,\hat w_{z,t};w^t​(c~)=w^g,t​+γc~​w^z,t​;

c~=1\tilde c = 1c~=1 is the plug-in rule. The expected out-of-sample utility E[U(w^t(c~))]E[U(\hat w_t(\tilde c))]E[U(w^t​(c~))] evaluates UUU at the true μ\muμ, Σ\SigmaΣ and averages over the sample. The five random quantities μg,t=w^g,t′μ\mu_{g,t} = \hat w_{g,t}'\muμg,t​=w^g,t′​μ, μz,t=w^z,t′μ\mu_{z,t} = \hat w_{z,t}'\muμz,t​=w^z,t′​μ, σg,t2=w^g,t′Σw^g,t\sigma^2_{g,t} = \hat w_{g,t}'\Sigma\hat w_{g,t}σg,t2​=w^g,t′​Σw^g,t​, σz,t2=w^z,t′Σw^z,t\sigma^2_{z,t} = \hat w_{z,t}'\Sigma\hat w_{z,t}σz,t2​=w^z,t′​Σw^z,t​ and σgz,t=w^g,t′Σw^z,t\sigma_{gz,t} = \hat w_{g,t}'\Sigma\hat w_{z,t}σgz,t​=w^g,t′​Σw^z,t​ determine it.

Formalization targets

Goal: the optimal combining coefficient (§2.3, eqs. (20)–(21))

For N≥2N \ge 2N≥2 and h>N+3h > N + 3h>N+3, with

k=(h−N)(h−N−3)h(h−2),c~∗=kψ2ψ2+N−1h,k = \frac{(h-N)(h-N-3)}{h(h-2)}, \qquad \tilde c^* = \frac{k\psi^2}{\psi^2 + \frac{N-1}{h}},k=h(h−2)(h−N)(h−N−3)​,c~∗=ψ2+hN−1​kψ2​,

the coefficient c~∗\tilde c^*c~∗ is the unique maximizer of c~↦E[U(w^t(c~))]\tilde c \mapsto E[U(\hat w_t(\tilde c))]c~↦E[U(w^t​(c~))] over R\mathbb RR, and 0≤c~∗<10 \le \tilde c^* < 10≤c~∗<1, with c~∗>0\tilde c^* > 0c~∗>0 when ψ2>0\psi^2 > 0ψ2>0.

Lemma 1 (eq. (17))

For h>N+3h > N + 3h>N+3 and every constant c~\tilde cc~,

E[U(w^t(c~))]=μg−γ(h−2)σg22(h−N−1)+hγ(h−N−1)[c~ψ2−c~2(h−2)(hψ2+N−1)2(h−N)(h−N−3)].E[U(\hat w_t(\tilde c))] = \mu_g - \frac{\gamma(h-2)\sigma_g^2}{2(h-N-1)} + \frac{h}{\gamma(h-N-1)}\left[\tilde c\psi^2 - \frac{\tilde c^2(h-2)(h\psi^2+N-1)}{2(h-N)(h-N-3)}\right].E[U(w^t​(c~))]=μg​−2(h−N−1)γ(h−2)σg2​​+γ(h−N−1)h​[c~ψ2−2(h−N)(h−N−3)c~2(h−2)(hψ2+N−1)​].

The moments (A9)–(A13) and the auxiliary moments

E[μg,t]=μg,E[μz,t]=hψ2h−N−1,E[σg,t2]=(h−2)σg2h−N−1,E[\mu_{g,t}] = \mu_g,\quad E[\mu_{z,t}] = \frac{h\psi^2}{h-N-1},\quad E[\sigma^2_{g,t}] = \frac{(h-2)\sigma_g^2}{h-N-1},E[μg,t​]=μg​,E[μz,t​]=h−N−1hψ2​,E[σg,t2​]=h−N−1(h−2)σg2​​, E[σz,t2]=h(h−2)(hψ2+N−1)(h−N)(h−N−1)(h−N−3),E[σgz,t]=0,E[\sigma^2_{z,t}] = \frac{h(h-2)(h\psi^2+N-1)}{(h-N)(h-N-1)(h-N-3)},\quad E[\sigma_{gz,t}] = 0,E[σz,t2​]=(h−N)(h−N−1)(h−N−3)h(h−2)(hψ2+N−1)​,E[σgz,t​]=0,

together with the first and second moments of the auxiliary variables y1y_1y1​, y2y_2y2​ of Proposition 1 that the proof of Lemma 1 uses.

Significance

The result gives a closed-form, implementable-in-principle correction to the plug-in rule: since c~∗<1\tilde c^* < 1c~∗<1, the investor should always under-weight the estimated zero-investment portfolio, by a factor that depends only on hhh, NNN and ψ2\psi^2ψ2. Replacing ψ2\psi^2ψ2 by an adjusted estimator gives the paper's feasible rules (§2.4, §3), which are compared empirically in §4. The moment formulas (A9)–(A13) are of independent use: they give the exact out-of-sample mean and variance of the sample GMV and zero-investment portfolios, which recur in the shrinkage literature (for instance Lassance, Martín-Utrera and Simaan, 2024, who build on this paper's Proposition 1).

The result is proved in the paper, but the proof rests on Proposition 1, a stochastic representation of the out-of-sample moments whose detailed proof is in an online appendix. No machine-checked proof exists. On Prove2Me, Proposition 1 is posed (Open) as RiskEU.OOSUVar.kan_representation in Lassance et al.'s restatement, together with special cases (eq_IA60, eq_IA49) of the combinations μg,t+(κ/γ)μz,t\mu_{g,t} + (\kappa/\gamma)\mu_{z,t}μg,t​+(κ/γ)μz,t​ and of the portfolio variance for κ∈[0,1]\kappa \in [0, 1]κ∈[0,1] and h>N+7h > N + 7h>N+7. The closed-form vertex of the quadratic (17) is already proved there (RiskEU.RobustShrink.proposition_IA_1_3). What this mission adds is the statement about the actual expectation over the Gaussian sample, for all real c~\tilde cc~, under the paper's own threshold h>N+3h > N + 3h>N+3, with uniqueness of the maximizer.

Difficulty

Once Lemma 1 is available, the goal is the vertex of a concave quadratic. The difficulty is Lemma 1 itself: computing expectations of quadratic forms in Σ^t−1\hat\Sigma_t^{-1}Σ^t−1​ and in the normalized vector Σ^t−11N/(1N′Σ^t−11N)\hat\Sigma_t^{-1}1_N/(1_N'\hat\Sigma_t^{-1}1_N)Σ^t−1​1N​/(1N′​Σ^t−1​1N​). The weights are ratios of dependent random quantities, so linearity of expectation does not apply directly, and inverse-Wishart moment formulas alone do not cover the ratio in w^g,t\hat w_{g,t}w^g,t​. The threshold h>N+3h > N + 3h>N+3 is Lemma 1's hypothesis; the factor h−N−3h-N-3h−N−3 in the denominator of (A12) shows that it is what keeps the expected variance of the estimated zero-investment portfolio finite, so integrability is part of the content.

Formalization scope

The model is the published definition RiskEU.OOSUVar.Setting: Market N carries μ\muμ, Σ\SigmaΣ, γ\gammaγ; sigmaG2, muG, psi2, U, sampleMean, sampleCov (divided by hhh), wHatG, wHatZ and IsGaussianSample are the objects above (that setting calls the window TTT; here it is hhh). The auxiliary family of Proposition 1 and y1y_1y1​, y2y_2y2​ come from the published RiskEU.OOSUVar.KanRepresentation. The mission's own definitions (KanCombine.Optimal.Model) add the standing assumptions, the combining portfolio, the five sample moments, the expected utility, kkk and c~∗\tilde c^*c~∗.

Conventions committed to:

  • N≥2N \ge 2N≥2, Σ≻0\Sigma \succ 0Σ≻0 and γ>0\gamma > 0γ>0 are explicit hypotheses (implicit in the paper); h>N+3h > N + 3h>N+3 is Lemma 1's. The yyy-moment milestone also assumes N>3N > 3N>3, as Proposition 1 does.
  • c~\tilde cc~ ranges over all of R\mathbb RR, and "the optimal value" is stated as a unique maximizer.
  • Every expectation identity asserts integrability: a Lean Bochner integral of a non-integrable function is 000.
  • Lean's matrix inverse is 000 on singular matrices; Σ^t\hat\Sigma_tΣ^t​ is almost surely nonsingular for h>Nh > Nh>N, so this does not change any expectation.
  • The page's "0<c~∗<10 < \tilde c^* < 10<c~∗<1" fails at ψ2=0\psi^2 = 0ψ2=0, where c~∗=0\tilde c^* = 0c~∗=0; the goal states 0≤c~∗<10 \le \tilde c^* < 10≤c~∗<1 and c~∗>0\tilde c^* > 0c~∗>0 under ψ2>0\psi^2 > 0ψ2>0.

The goal is about the integral over the Gaussian sample. Stating it about the closed-form right-hand side of (17) would reduce it to the vertex of a quadratic, which is already proved, and is ruled out. The hypotheses are satisfiable: N=2N = 2N=2, h=6h = 6h=6, μ=(0,1)\mu = (0, 1)μ=(0,1), Σ=I\Sigma = IΣ=I, γ=1\gamma = 1γ=1 meets them with the product Gaussian sample, and gives c~∗=1/8\tilde c^* = 1/8c~∗=1/8.

A complete development needs Wishart and inverse-Wishart theory (the Bartlett decomposition, moments of chi-squared ratios) and a formal version of Proposition 1. These are reusable well beyond this mission; contributions proving (A9)–(A13) by any route, including directly from inverse-Wishart moments, are welcome.

Selected references

  • R. Kan, X. Wang and G. Zhou, Optimal portfolio choice with estimation risk: No risk-free asset case, Management Science 68(3), 2022 (cited from the submitted manuscript, November 2020). https://doi.org/10.1287/mnsc.2021.3989 ; https://ssrn.com/abstract=2819254
  • R. Kan and G. Zhou, Optimal portfolio choice with parameter uncertainty, Journal of Financial and Quantitative Analysis 42(3), 2007. https://doi.org/10.1017/S0022109000004129
  • H. Markowitz, Portfolio selection, Journal of Finance 7(1), 1952. https://doi.org/10.1111/j.1540-6261.1952.tb01525.x
  • N. Lassance, A. Martín-Utrera and M. Simaan, The risk of expected utility under parameter uncertainty, Management Science, 2024. https://doi.org/10.1287/mnsc.2023.00178
  • R. J. Muirhead, Aspects of Multivariate Statistical Theory, Wiley, 1982. https://doi.org/10.1002/9780470316559
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Quantum Information·Captain: Goku

A provable quantum advantage for approximate optimization via decoded quantum interferometryResearch Paper

Motivation

A provable quantum advantage for approximate optimization via decoded quantum interferometry establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Fix a rational rate R∈(0,1)R\in(0,1)R∈(0,1). An admissible block count M>0M>0M>0 satisfies M+1=2uM+1=2^uM+1=2u for an integer u>0u>0u>0, and K=⌊RN⌋≥hK=\lfloor RN\rfloor\ge hK=⌊RN⌋≥h, where h=M+2h=M+2h=M+2, N=hMN=hMN=hM and q=N+1=(M+1)2q=N+1=(M+1)^2q=N+1=(M+1)2. Work over the publicly represented characteristic-two field Fq\mathbb F_qFq​, with a fixed public primitive element γ\gammaγ. Put J=⌊K/h⌋J=\lfloor K/h\rfloorJ=⌊K/h⌋ and Σ=Fqh\Sigma=\mathbb F_q^hΣ=Fqh​. A promised instance consists of arbitrary sets Ai⊆ΣA_i\subseteq\SigmaAi​⊆Σ with ∣Ai∣=∣Σ∣/2|A_i|=|\Sigma|/2∣Ai​∣=∣Σ∣/2, accessed only through separately callable fixed-block XOR membership oracles. Each call chooses its block classically and may query a superposition of whole symbols.

A coefficient vector x∈FqKx\in\mathbb F_q^Kx∈FqK​ represents the polynomial Qx(Y)=∑j=0K−1xjYjQ_x(Y)=\sum_{j=0}^{K-1}x_jY^jQx​(Y)=∑j=0K−1​xj​Yj, including the zero polynomial. Its score is

score⁡A(Qx)=1M∑i=0M−11 ⁣[(Qx(γih+j))j=0h−1∈Ai].\operatorname{score}_{\mathcal A}(Q_x)=\frac1M\sum_{i=0}^{M-1} \mathbf1\!\left[(Q_x(\gamma^{ih+j}))_{j=0}^{h-1}\in A_i\right].scoreA​(Qx​)=M1​i=0∑M−1​1[(Qx​(γih+j))j=0h−1​∈Ai​].

Define

αC(R)=1+R2,αQ(R)=1+R(2−R)2.\alpha_C(R)=\frac{1+R}{2},\qquad \alpha_Q(R)=\frac{1+\sqrt{R(2-R)}}2.αC​(R)=21+R​,αQ​(R)=21+R(2−R)​​.
  1. There is a uniform quantum polynomial-time DQI family using one query to each fixed-block oracle, at most MMM queries in total. Its expected score converges to αQ(R)\alpha_Q(R)αQ​(R) uniformly over every promised instance:
∀ϵ>0 ∃M0 ∀ admissible M≥M0 ∀A,∣E[score⁡A(QDQI)]−αQ(R)∣≤ϵ.\forall\epsilon>0\ \exists M_0\ \forall\text{ admissible }M\ge M_0\ \forall\mathcal A,\quad \left|\mathbb E[\operatorname{score}_{\mathcal A}(Q_{\rm DQI})]-\alpha_Q(R)\right|\le\epsilon.∀ϵ>0 ∃M0​ ∀ admissible M≥M0​ ∀A,∣E[scoreA​(QDQI​)]−αQ​(R)∣≤ϵ.

The construction uses the conventional unfolded scalar GRS dual syndrome decoder at cutoff ℓ=⌊(J−1)/2⌋\ell=\lfloor(J-1)/2\rfloorℓ=⌊(J−1)/2⌋, strictly below half its scalar minimum distance, the explicit top-window layer weights, and synthesis accuracy M−2M^{-2}M−2. Its polynomial resource bounds and classical circuit constructor are independent of the acceptance sets.

  1. A randomized polynomial-time implementation of Prange's information-set algorithm makes at most 4M4M4M membership queries in the worst case. It samples uniformly with replacement until obtaining accepted targets in the first JJJ blocks, interpolates their hJhJhJ evaluations, and returns zero if the total trial cap is exhausted. When the sets AiA_iAi​ are sampled independently and uniformly among half-size subsets, independently of the algorithm's randomness,
∀ϵ,δ>0 ∃M0 ∀ admissible M≥M0,Pr⁡ ⁣[∣score⁡(QPrange)−αC(R)∣>ϵ]≤δ.\forall\epsilon,\delta>0\ \exists M_0\ \forall\text{ admissible }M\ge M_0,\quad \Pr\!\left[\left|\operatorname{score}(Q_{\rm Prange})-\alpha_C(R)\right|>\epsilon\right]\le\delta.∀ϵ,δ>0 ∃M0​ ∀ admissible M≥M0​,Pr[∣score(QPrange​)−αC​(R)∣>ϵ]≤δ.
  1. For each fixed 0<η<1−αC(R)0<\eta<1-\alpha_C(R)0<η<1−αC​(R), there are θ,c>0\theta,c>0θ,c>0 and M0≥2M_0\ge2M0​≥2, depending only on R,ηR,\etaR,η, such that every admissible M≥M0M\ge M_0M≥M0​ and every randomized classical algorithm with worst-case query budget T≤exp⁡(θM/log⁡M)T\le\exp(\theta M/\log M)T≤exp(θM/logM) satisfy
Pr⁡[score⁡(A(ω))≥αC(R)+η]≤e−cM.\Pr[\operatorname{score}(A(\omega))\ge\alpha_C(R)+\eta]\le e^{-cM}.Pr[score(A(ω))≥αC​(R)+η]≤e−cM.

The probability is over the same sampled acceptance sets and independent algorithm randomness. Computation between queries and arbitrary finite advice are unrestricted, provided the description and advice are fixed before sampling.

This result separates the approximation scores attainable through the same whole-symbol membership interface. The quantum assertion is an expectation guarantee for every promised oracle; the classical assertions are distributional.

Formalization Note A fixed effective polynomial-basis binary field representation and uniform compilation over {H,T,CNOT}\{H,T,\mathrm{CNOT}\}{H,T,CNOT} make the implicit public representation and polynomial runtime concrete. The DQI state, its coefficient output wires and its query count are tied to one circuit. The sampled probabilities are finite uniform averages of normalized classical output laws.

Target

Theorem 1 (continues on PDF p.16)

Fix a rational rate R∈(0,1)R\in(0,1)R∈(0,1). An admissible block count M>0M>0M>0 satisfies M+1=2uM+1=2^uM+1=2u for an integer u>0u>0u>0, and K=⌊RN⌋≥hK=\lfloor RN\rfloor\ge hK=⌊RN⌋≥h, where h=M+2h=M+2h=M+2, N=hMN=hMN=hM and q=N+1=(M+1)2q=N+1=(M+1)^2q=N+1=(M+1)2. Work over the publicly represented characteristic-two field Fq\mathbb F_qFq​, with a fixed public primitive element γ\gammaγ. Put J=⌊K/h⌋J=\lfloor K/h\rfloorJ=⌊K/h⌋ and Σ=Fqh\Sigma=\mathbb F_q^hΣ=Fqh​. A promised instance consists of arbitrary sets Ai⊆ΣA_i\subseteq\SigmaAi​⊆Σ with ∣Ai∣=∣Σ∣/2|A_i|=|\Sigma|/2∣Ai​∣=∣Σ∣/2, accessed only through separately callable fixed-block XOR membership oracles. Each call chooses its block classically and may query a superposition of whole symbols.

A coefficient vector x∈FqKx\in\mathbb F_q^Kx∈FqK​ represents the polynomial Qx(Y)=∑j=0K−1xjYjQ_x(Y)=\sum_{j=0}^{K-1}x_jY^jQx​(Y)=∑j=0K−1​xj​Yj, including the zero polynomial. Its score is

score⁡A(Qx)=1M∑i=0M−11 ⁣[(Qx(γih+j))j=0h−1∈Ai].\operatorname{score}_{\mathcal A}(Q_x)=\frac1M\sum_{i=0}^{M-1} \mathbf1\!\left[(Q_x(\gamma^{ih+j}))_{j=0}^{h-1}\in A_i\right].scoreA​(Qx​)=M1​i=0∑M−1​1[(Qx​(γih+j))j=0h−1​∈Ai​].

Define

αC(R)=1+R2,αQ(R)=1+R(2−R)2.\alpha_C(R)=\frac{1+R}{2},\qquad \alpha_Q(R)=\frac{1+\sqrt{R(2-R)}}2.αC​(R)=21+R​,αQ​(R)=21+R(2−R)​​.
  1. There is a uniform quantum polynomial-time DQI family using one query to each fixed-block oracle, at most MMM queries in total. Its expected score converges to αQ(R)\alpha_Q(R)αQ​(R) uniformly over every promised instance:
∀ϵ>0 ∃M0 ∀ admissible M≥M0 ∀A,∣E[score⁡A(QDQI)]−αQ(R)∣≤ϵ.\forall\epsilon>0\ \exists M_0\ \forall\text{ admissible }M\ge M_0\ \forall\mathcal A,\quad \left|\mathbb E[\operatorname{score}_{\mathcal A}(Q_{\rm DQI})]-\alpha_Q(R)\right|\le\epsilon.∀ϵ>0 ∃M0​ ∀ admissible M≥M0​ ∀A,∣E[scoreA​(QDQI​)]−αQ​(R)∣≤ϵ.

The construction uses the conventional unfolded scalar GRS dual syndrome decoder at cutoff ℓ=⌊(J−1)/2⌋\ell=\lfloor(J-1)/2\rfloorℓ=⌊(J−1)/2⌋, strictly below half its scalar minimum distance, the explicit top-window layer weights, and synthesis accuracy M−2M^{-2}M−2. Its polynomial resource bounds and classical circuit constructor are independent of the acceptance sets.

  1. A randomized polynomial-time implementation of Prange's information-set algorithm makes at most 4M4M4M membership queries in the worst case. It samples uniformly with replacement until obtaining accepted targets in the first JJJ blocks, interpolates their hJhJhJ evaluations, and returns zero if the total trial cap is exhausted. When the sets AiA_iAi​ are sampled independently and uniformly among half-size subsets, independently of the algorithm's randomness,
∀ϵ,δ>0 ∃M0 ∀ admissible M≥M0,Pr⁡ ⁣[∣score⁡(QPrange)−αC(R)∣>ϵ]≤δ.\forall\epsilon,\delta>0\ \exists M_0\ \forall\text{ admissible }M\ge M_0,\quad \Pr\!\left[\left|\operatorname{score}(Q_{\rm Prange})-\alpha_C(R)\right|>\epsilon\right]\le\delta.∀ϵ,δ>0 ∃M0​ ∀ admissible M≥M0​,Pr[∣score(QPrange​)−αC​(R)∣>ϵ]≤δ.
  1. For each fixed 0<η<1−αC(R)0<\eta<1-\alpha_C(R)0<η<1−αC​(R), there are θ,c>0\theta,c>0θ,c>0 and M0≥2M_0\ge2M0​≥2, depending only on R,ηR,\etaR,η, such that every admissible M≥M0M\ge M_0M≥M0​ and every randomized classical algorithm with worst-case query budget T≤exp⁡(θM/log⁡M)T\le\exp(\theta M/\log M)T≤exp(θM/logM) satisfy
Pr⁡[score⁡(A(ω))≥αC(R)+η]≤e−cM.\Pr[\operatorname{score}(A(\omega))\ge\alpha_C(R)+\eta]\le e^{-cM}.Pr[score(A(ω))≥αC​(R)+η]≤e−cM.

The probability is over the same sampled acceptance sets and independent algorithm randomness. Computation between queries and arbitrary finite advice are unrestricted, provided the description and advice are fixed before sampling.

This result separates the approximation scores attainable through the same whole-symbol membership interface. The quantum assertion is an expectation guarantee for every promised oracle; the classical assertions are distributional.

Formalization Note A fixed effective polynomial-basis binary field representation and uniform compilation over {H,T,CNOT}\{H,T,\mathrm{CNOT}\}{H,T,CNOT} make the implicit public representation and polynomial runtime concrete. The DQI state, its coefficient output wires and its query count are tied to one circuit. The sampled probabilities are finite uniform averages of normalized classical output laws.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • A provable quantum advantage for approximate optimization via decoded quantum interferometry, arXiv:2610.02145v2. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
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Quantum Information·Captain: Goku

An Optimal Quantum Linear Systems AlgorithmResearch Paper

Motivation

An Optimal Quantum Linear Systems Algorithm establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Consider the quantum linear systems problem for an invertible, complex, ddd-sparse N×NN\times NN×N matrix AAA, with 1≤d≤N1\le d\le N1≤d≤N, ∥A∥≤1\|A\|\le1∥A∥≤1, and ∥A−1∥≤κ\|A^{-1}\|\le\kappa∥A−1∥≤κ, where these are operator norms and κ\kappaκ is known. For a nonzero vector bbb, a supplied preparation circuit prepares ∣b⟩=b/∥b∥|b\rangle=b/\|b\|∣b⟩=b/∥b∥. The solver must output a success flag of probability at least 1/21/21/2 and, conditioned on success, a normalized reduced density matrix within trace distance ϵ\epsilonϵ of ∣x⟩⟨x∣|x\rangle\langle x|∣x⟩⟨x∣, where ∣x⟩=A−1b/∥A−1b∥|x\rangle=A^{-1}b/\|A^{-1}b\|∣x⟩=A−1b/∥A−1b∥. Both AAA and A†A^\daggerA† have reversible row-location and XOR entry-value oracles; the ddd locations listed in each row are distinct, cover all nonzeros, and may include zeros. Only matrix-oracle calls count, including inverse and controlled calls. Supplied preparation operations and known quantum operations are free.

Let Q(d,κ,ϵ)Q(d,\kappa,\epsilon)Q(d,κ,ϵ) be the supremum over positive dimensions N≥dN\ge dN≥d and public finite exact entry encodings of the least natural worst-case matrix-query budget of a solver correct for every compatible promised input and oracle completion. Solvers are chosen before the hidden matrix, vector, and oracle completions. Empty sets of feasible budgets and unbounded suprema retain +∞+\infty+∞. There exist absolute constants c,C>0c,C>0c,C>0, κ0≥1\kappa_0\ge1κ0​≥1, d0≥1d_0\ge1d0​≥1, and 0<ϵ0<10<\epsilon_0<10<ϵ0​<1 such that, for every κ≥κ0\kappa\ge\kappa_0κ≥κ0​, d≥d0d\ge d_0d≥d0​, and 0<ϵ≤ϵ00<\epsilon\le\epsilon_00<ϵ≤ϵ0​,

cκdlog⁡(1/ϵ)≤Q(d,κ,ϵ)≤Cκdlog⁡(1/ϵ).c\kappa\sqrt d\log(1/\epsilon)\le Q(d,\kappa,\epsilon)\le C\kappa\sqrt d\log(1/\epsilon).cκd​log(1/ϵ)≤Q(d,κ,ϵ)≤Cκd​log(1/ϵ).

This gives matching upper and worst-case lower bounds jointly in sparsity, inverse-norm bound, and precision. The constants and thresholds are independent of dimension, encoding, and input.

Formalization Note Complexity is represented in R≥0∪{+∞}\mathbb R_{\ge0}\cup\{+\infty\}R≥0​∪{+∞} using the frozen OptimalQLSP.queryComplexity. General matrices and general positive dimensions are retained; the Hermitian reduction and power-of-two registers used inside the proof do not restrict the headline.

Target

Theorem 1, equation (6)

Consider the quantum linear systems problem for an invertible, complex, ddd-sparse N×NN\times NN×N matrix AAA, with 1≤d≤N1\le d\le N1≤d≤N, ∥A∥≤1\|A\|\le1∥A∥≤1, and ∥A−1∥≤κ\|A^{-1}\|\le\kappa∥A−1∥≤κ, where these are operator norms and κ\kappaκ is known. For a nonzero vector bbb, a supplied preparation circuit prepares ∣b⟩=b/∥b∥|b\rangle=b/\|b\|∣b⟩=b/∥b∥. The solver must output a success flag of probability at least 1/21/21/2 and, conditioned on success, a normalized reduced density matrix within trace distance ϵ\epsilonϵ of ∣x⟩⟨x∣|x\rangle\langle x|∣x⟩⟨x∣, where ∣x⟩=A−1b/∥A−1b∥|x\rangle=A^{-1}b/\|A^{-1}b\|∣x⟩=A−1b/∥A−1b∥. Both AAA and A†A^\daggerA† have reversible row-location and XOR entry-value oracles; the ddd locations listed in each row are distinct, cover all nonzeros, and may include zeros. Only matrix-oracle calls count, including inverse and controlled calls. Supplied preparation operations and known quantum operations are free.

Let Q(d,κ,ϵ)Q(d,\kappa,\epsilon)Q(d,κ,ϵ) be the supremum over positive dimensions N≥dN\ge dN≥d and public finite exact entry encodings of the least natural worst-case matrix-query budget of a solver correct for every compatible promised input and oracle completion. Solvers are chosen before the hidden matrix, vector, and oracle completions. Empty sets of feasible budgets and unbounded suprema retain +∞+\infty+∞. There exist absolute constants c,C>0c,C>0c,C>0, κ0≥1\kappa_0\ge1κ0​≥1, d0≥1d_0\ge1d0​≥1, and 0<ϵ0<10<\epsilon_0<10<ϵ0​<1 such that, for every κ≥κ0\kappa\ge\kappa_0κ≥κ0​, d≥d0d\ge d_0d≥d0​, and 0<ϵ≤ϵ00<\epsilon\le\epsilon_00<ϵ≤ϵ0​,

cκdlog⁡(1/ϵ)≤Q(d,κ,ϵ)≤Cκdlog⁡(1/ϵ).c\kappa\sqrt d\log(1/\epsilon)\le Q(d,\kappa,\epsilon)\le C\kappa\sqrt d\log(1/\epsilon).cκd​log(1/ϵ)≤Q(d,κ,ϵ)≤Cκd​log(1/ϵ).

This gives matching upper and worst-case lower bounds jointly in sparsity, inverse-norm bound, and precision. The constants and thresholds are independent of dimension, encoding, and input.

Formalization Note Complexity is represented in R≥0∪{+∞}\mathbb R_{\ge0}\cup\{+\infty\}R≥0​∪{+∞} using the frozen OptimalQLSP.queryComplexity. General matrices and general positive dimensions are retained; the Hermitian reduction and power-of-two registers used inside the proof do not restrict the headline.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • An Optimal Quantum Linear Systems Algorithm, arXiv:2609.35660v1. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Machine LearningQuantum Information·Captain: Goku

Sample-optimal learning of stabilizer statesResearch Paper

Motivation

Sample-optimal learning of stabilizer states establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let n≥1n\ge 1n≥1 be the number of qubits and let 0<δ<1/80<\delta<1/80<δ<1/8 be the allowed failure probability. An unknown normalized pure stabilizer state ∣ψ⟩|\psi\rangle∣ψ⟩ is provided as identical copies. Let Lδ(n)L_\delta(n)Lδ​(n) be the least number of copies with which one quantum procedure can identify every such state with probability at least 1−δ1-\delta1−δ. The minimum permits arbitrary collective measurements, ancillas, internal randomness and adaptivity. Identification means outputting a valid tableau of nnn independent signed Pauli generators whose common +1+1+1 eigenspace is the input state; global phase and the choice of generators are irrelevant. Then

n+⌈log⁡21δ⌉−3≤Lδ(n)≤n+⌈log⁡21δ⌉+4.n+\left\lceil\log_2\frac1\delta\right\rceil-3 \le L_\delta(n)\le n+\left\lceil\log_2\frac1\delta\right\rceil+4.n+⌈log2​δ1​⌉−3≤Lδ​(n)≤n+⌈log2​δ1​⌉+4.

Furthermore, for every such nnn and δ\deltaδ, there is a quantum learner receiving at most n+⌈log⁡2(1/δ)⌉+4n+\lceil\log_2(1/\delta)\rceil+4n+⌈log2​(1/δ)⌉+4 copies and retaining them through adaptive operations, which identifies every input stabilizer state with failure probability at most δ\deltaδ. There are absolute constants C>0C>0C>0 and s0≥1s_0\ge1s0​≥1, independent of nnn, δ\deltaδ and the input state, such that this learner has computational time

time⁡≤Cn(n+ln⁡(1/δ))4whenever n+ln⁡(1/δ)≥s0.\operatorname{time}\le Cn\bigl(n+\ln(1/\delta)\bigr)^4 \qquad\text{whenever }n+\ln(1/\delta)\ge s_0.time≤Cn(n+ln(1/δ))4whenever n+ln(1/δ)≥s0​.

Time counts elementary quantum gates, measurements, fair coins and Boolean operations, including classical and reversible arithmetic, finite-precision rotation synthesis and tableau reconstruction. The sample and success bounds have no asymptotic threshold. This determines the leading sample coefficient to be one and attains the bound with an efficient learner.

Formalization Note The minimum is represented in N∪{∞}\mathbb N\cup\{\infty\}N∪{∞}, with an empty feasible set assigned ∞\infty∞; the upper bound implies finiteness. The lower inequality is written as n+⌈log⁡2(1/δ)⌉≤Lδ(n)+3n+\lceil\log_2(1/\delta)\rceil\le L_\delta(n)+3n+⌈log2​(1/δ)⌉≤Lδ​(n)+3 to avoid natural subtraction. The theorem's printed statement leaves the qubit domain implicit; n≥1n\ge1n≥1 follows the lower-bound proof on PDF p.7, since the zero-qubit state requires zero copies.

Target

Theorem 1

Let n≥1n\ge 1n≥1 be the number of qubits and let 0<δ<1/80<\delta<1/80<δ<1/8 be the allowed failure probability. An unknown normalized pure stabilizer state ∣ψ⟩|\psi\rangle∣ψ⟩ is provided as identical copies. Let Lδ(n)L_\delta(n)Lδ​(n) be the least number of copies with which one quantum procedure can identify every such state with probability at least 1−δ1-\delta1−δ. The minimum permits arbitrary collective measurements, ancillas, internal randomness and adaptivity. Identification means outputting a valid tableau of nnn independent signed Pauli generators whose common +1+1+1 eigenspace is the input state; global phase and the choice of generators are irrelevant. Then

n+⌈log⁡21δ⌉−3≤Lδ(n)≤n+⌈log⁡21δ⌉+4.n+\left\lceil\log_2\frac1\delta\right\rceil-3 \le L_\delta(n)\le n+\left\lceil\log_2\frac1\delta\right\rceil+4.n+⌈log2​δ1​⌉−3≤Lδ​(n)≤n+⌈log2​δ1​⌉+4.

Furthermore, for every such nnn and δ\deltaδ, there is a quantum learner receiving at most n+⌈log⁡2(1/δ)⌉+4n+\lceil\log_2(1/\delta)\rceil+4n+⌈log2​(1/δ)⌉+4 copies and retaining them through adaptive operations, which identifies every input stabilizer state with failure probability at most δ\deltaδ. There are absolute constants C>0C>0C>0 and s0≥1s_0\ge1s0​≥1, independent of nnn, δ\deltaδ and the input state, such that this learner has computational time

time⁡≤Cn(n+ln⁡(1/δ))4whenever n+ln⁡(1/δ)≥s0.\operatorname{time}\le Cn\bigl(n+\ln(1/\delta)\bigr)^4 \qquad\text{whenever }n+\ln(1/\delta)\ge s_0.time≤Cn(n+ln(1/δ))4whenever n+ln(1/δ)≥s0​.

Time counts elementary quantum gates, measurements, fair coins and Boolean operations, including classical and reversible arithmetic, finite-precision rotation synthesis and tableau reconstruction. The sample and success bounds have no asymptotic threshold. This determines the leading sample coefficient to be one and attains the bound with an efficient learner.

Formalization Note The minimum is represented in N∪{∞}\mathbb N\cup\{\infty\}N∪{∞}, with an empty feasible set assigned ∞\infty∞; the upper bound implies finiteness. The lower inequality is written as n+⌈log⁡2(1/δ)⌉≤Lδ(n)+3n+\lceil\log_2(1/\delta)\rceil\le L_\delta(n)+3n+⌈log2​(1/δ)⌉≤Lδ​(n)+3 to avoid natural subtraction. The theorem's printed statement leaves the qubit domain implicit; n≥1n\ge1n≥1 follows the lower-bound proof on PDF p.7, since the zero-qubit state requires zero copies.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Sample-optimal learning of stabilizer states, arXiv:2609.10974v1. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Information·Captain: Goku

Efficient Exact Quantum Sampling from the Sun-Wootters Distribution for Optimal Polynomial IntersectionResearch Paper

Motivation

Efficient Exact Quantum Sampling from the Sun-Wootters Distribution for Optimal Polynomial Intersection establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let ppp be prime, 1≤n<m≤p1\le n<m\le p1≤n<m≤p, and let α1,…,αm∈Fp\alpha_1,\ldots,\alpha_m\in\mathbb F_pα1​,…,αm​∈Fp​ be distinct public evaluation points. Every hidden set Si⊂FpS_i\subset\mathbb F_pSi​⊂Fp​ has the same known cardinality ccc, with 0<c<p0<c<p0<c<p. Put ρ=c/p\rho=c/pρ=c/p, Bij=αijB_{ij}=\alpha_i^jBij​=αij​ for j=0,…,n−1j=0,\ldots,n-1j=0,…,n−1, and H=BTH=B^{\mathsf T}H=BT. A coefficient vector x∈Fpnx\in\mathbb F_p^nx∈Fpn​ represents the polynomial Qx(T)=∑j=0n−1xjTjQ_x(T)=\sum_{j=0}^{n-1}x_jT^jQx​(T)=∑j=0n−1​xj​Tj; its satisfaction ratio is s(x)=m−1∣{i:Qx(αi)∈Si}∣s(x)=m^{-1}|\{i:Q_x(\alpha_i)\in S_i\}|s(x)=m−1∣{i:Qx​(αi​)∈Si​}∣. Access is through the indexed XOR oracle OS∣i,a,b⟩=∣i,a,b⊕1a∈Si⟩O_S|i,a,b\rangle=|i,a,b\oplus\mathbf1_{a\in S_i}\rangleOS​∣i,a,b⟩=∣i,a,b⊕1a∈Si​​⟩, with arbitrary full unitary behavior on invalid encodings.

For an integer cutoff 3≤ℓ≤m3\le\ell\le m3≤ℓ≤m, set σ=⌊log⁡log⁡ℓ⌋\sigma=\lfloor\log\log\ell\rfloorσ=⌊loglogℓ⌋, K={k∈{0,…,m}:ℓ−σ≤k≤ℓ}K=\{k\in\{0,\ldots,m\}:\ell-\sigma\le k\le\ell\}K={k∈{0,…,m}:ℓ−σ≤k≤ℓ}, and uk=(mk)−1/21k∈Ku_k=\binom mk^{-1/2}\mathbf1_{k\in K}uk​=(km​)−1/21k∈K​. Define gi(a)=(1a∈Si−ρ)/ρ(1−ρ)g_i(a)=(\mathbf1_{a\in S_i}-\rho)/\sqrt{\rho(1-\rho)}gi​(a)=(1a∈Si​​−ρ)/ρ(1−ρ)​, g^i(z)=p−1∑agi(a)e−2πiaz/p\widehat g_i(z)=p^{-1}\sum_a g_i(a)e^{-2\pi iaz/p}g​i​(z)=p−1∑a​gi​(a)e−2πiaz/p, qk(x)=∑∣T∣=k∏i∈Tgi((Bx)i)q_k(x)=\sum_{|T|=k}\prod_{i\in T}g_i((Bx)_i)qk​(x)=∑∣T∣=k​∏i∈T​gi​((Bx)i​) and F(x)=∑k∈Kukqk(x)F(x)=\sum_{k\in K}u_kq_k(x)F(x)=∑k∈K​uk​qk​(x). On its positive-denominator domain the Sun–Wootters law is

Pu(x)=∣F(x)∣2∑z∣F(z)∣2.P_u(x)=\frac{|F(x)|^2}{\sum_z|F(z)|^2}.Pu​(x)=∑z​∣F(z)∣2∣F(x)∣2​.

Write ay=uwt(y)∏i:yi≠0g^i(yi)a_y=u_{\mathrm{wt}(y)}\prod_{i:y_i\ne0}\widehat g_i(y_i)ay​=uwt(y)​∏i:yi​=0​g​i​(yi​), As=∑Hy=s, wt(y)∈KayA_s=\sum_{Hy=s,\,\mathrm{wt}(y)\in K}a_yAs​=∑Hy=s,wt(y)∈K​ay​, Z0=∑y∣ay∣2Z_0=\sum_y|a_y|^2Z0​=∑y​∣ay​∣2, and ZI=∑s∣As∣2Z_I=\sum_s|A_s|^2ZI​=∑s​∣As​∣2. Suppose Z0>0Z_0>0Z0​>0 and the target denominator is positive. For every complete duplicate-free canonical shell list, padded to the same L=2qL=2^qL=2q slots for every syndrome, the ideal attempt prepares Z0−1/2∑yay∣y,Hy⟩Z_0^{-1/2}\sum_y a_y|y,Hy\rangleZ0−1/2​∑y​ay​∣y,Hy⟩, reversibly indexes and erases the error, applies H⊗qH^{\otimes q}H⊗q to the index, and postselects (J,Q)=(0q,1)(J,Q)=(0^q,1)(J,Q)=(0q,1) using a match flag. It then applies the positive-character Fourier transform on the syndrome. Its success and conditional law satisfy

pideal=ZILZ0,L(x∣success)=Pu,ZI=p−n∑x∣F(x)∣2.p_{\rm ideal}=\frac{Z_I}{LZ_0},\qquad \mathcal L(x\mid\text{success})=P_u,\qquad Z_I=p^{-n}\sum_x|F(x)|^2.pideal​=LZ0​ZI​​,L(x∣success)=Pu​,ZI​=p−nx∑​∣F(x)∣2.

This finite identity preserves cancellation within fibers and asserts no running-time bound for an arbitrary unpriced list. For normalized ideal and implemented full-register states, ideal success at least 1/(2L)1/(2L)1/(2L), vector error at most min⁡{1/(8L),η/(42L)}\min\{1/(8L),\eta/(4\sqrt{2L})\}min{1/(8L),η/(42L​)}, and final Fourier operator error at most η/2\eta/2η/2, implemented success is at least 1/(4L)1/(4L)1/(4L) and conditional total variation error is at most η\etaη.

Now consider public parameter families with m→∞m\to\inftym→∞, n/m→r=2μ∈(0,1]n/m\to r=2\mu\in(0,1]n/m→r=2μ∈(0,1], and c/p→1/2c/p\to1/2c/p→1/2. Constants, programs and preprocessing are uniform over all sets of the promised cardinality and every supplied membership oracle. Let h(t)=−tlog⁡t−(1−t)log⁡(1−t)h(t)=-t\log t-(1-t)\log(1-t)h(t)=−tlogt−(1−t)log(1−t), using natural logarithms and 0log⁡0=00\log0=00log0=0, and define

E(μ,δ)=(μ+δ)h ⁣(μμ+δ)+(1−μ−δ)h ⁣(μ1−μ−δ)−h(2μ),E(\mu,\delta)=(\mu+\delta)h\!\left(\frac\mu{\mu+\delta}\right)+(1-\mu-\delta)h\!\left(\frac\mu{1-\mu-\delta}\right)-h(2\mu),E(μ,δ)=(μ+δ)h(μ+δμ​)+(1−μ−δ)h(1−μ−δμ​)−h(2μ), G(μ,λ)=(1−2μ)log⁡2+h(2μ)−(4μ−1)h ⁣(λ4μ−1)−(2−4μ)h ⁣(2μ−λ2−4μ)+λlog⁡(2/π).G(\mu,\lambda)=(1-2\mu)\log2+h(2\mu)-(4\mu-1)h\!\left(\frac\lambda{4\mu-1}\right)-(2-4\mu)h\!\left(\frac{2\mu-\lambda}{2-4\mu}\right)+\lambda\log(2/\pi).G(μ,λ)=(1−2μ)log2+h(2μ)−(4μ−1)h(4μ−1λ​)−(2−4μ)h(2−4μ2μ−λ​)+λlog(2/π).

All denominators in these ratios must be nonzero and all entropy arguments must belong to [0,1][0,1][0,1]. Fix 0<μ<1/20<\mu<1/20<μ<1/2, a positive rational δ≤1/2−μ\delta\le1/2-\muδ≤1/2−μ, and λ\lambdaλ in that domain with E+G<0E+G<0E+G<0 and μ+δ<1−1−2μ\mu+\delta<1-\sqrt{1-2\mu}μ+δ<1−1−2μ​. Put ℓm=min⁡{⌊n/2+δm⌋,⌊m/2⌋}\ell_m=\min\{\lfloor n/2+\delta m\rfloor,\lfloor m/2\rfloor\}ℓm​=min{⌊n/2+δm⌋,⌊m/2⌋}. Eventually the target is well defined, complete canonical lists admit one polynomial common padding length, and ideal success is at least 1/(2L)1/(2L)1/(2L). For every η,β∈(0,1/2)\eta,\beta\in(0,1/2)η,β∈(0,1/2), a uniform quantum algorithm with time polynomial in m,log⁡p,log⁡(1/η),log⁡(1/β)m,\log p,\log(1/\eta),\log(1/\beta)m,logp,log(1/η),log(1/β) satisfies

Pr⁡[x=⊥]≤β,TV⁡(L(x∣x≠⊥),Pu,m)≤η.\Pr[x=\bot]\le\beta,\qquad \operatorname{TV}(\mathcal L(x\mid x\ne\bot),P_{u,m})\le\eta.Pr[x=⊥]≤β,TV(L(x∣x=⊥),Pu,m​)≤η.

For every fixed default vector, the defaulted law has total variation distance at most η+β\eta+\betaη+β from Pu,mP_{u,m}Pu,m​ and expected score at least SCL1/2(μ+δ)−am−η−β\mathrm{SCL}_{1/2}(\mu+\delta)-a_m-\eta-\betaSCL1/2​(μ+δ)−am​−η−β, for some nonnegative am→0a_m\to0am​→0 independent of the hidden sets; here SCL1/2(t)=1/2+t(1−t)\mathrm{SCL}_{1/2}(t)=1/2+\sqrt{t(1-t)}SCL1/2​(t)=1/2+t(1−t)​ on [0,1/2][0,1/2][0,1/2]. Preprocessing, synthesized gates, queries, measurements, reversible/classical work, and capped restarts are counted.

The two balanced consequences are retained:

  1. For each fixed r∈[249/400,1)r\in[249/400,1)r∈[249/400,1), a gap γr>0\gamma_r>0γr​>0 and a uniform algorithm are chosen before the sets or parameter family. Eventually E[s(x)]≥SCL1/2(r/2)+γr\mathbb E[s(x)]\ge\mathrm{SCL}_{1/2}(r/2)+\gamma_rE[s(x)]≥SCL1/2​(r/2)+γr​. For every fixed ε>0\varepsilon>0ε>0 and β∈(0,1)\beta\in(0,1)β∈(0,1), polynomially many samples give s(x)≥SCL1/2(r/2)+γr−εs(x)\ge\mathrm{SCL}_{1/2}(r/2)+\gamma_r-\varepsilons(x)≥SCL1/2​(r/2)+γr​−ε with probability at least 1−β1-\beta1−β.
  2. For every limiting r∈[3/4,1]r\in[3/4,1]r∈[3/4,1], a uniform polynomial-time algorithm has nonnegative em,bm→0e_m,b_m\to0em​,bm​→0 with Pr⁡[s(x)≥1−em]≥1−bm\Pr[s(x)\ge1-e_m]\ge1-b_mPr[s(x)≥1−em​]≥1−bm​. Its construction uses nm′=min⁡{n,⌊3m/4⌋}n'_m=\min\{n,\lfloor3m/4\rfloor\}nm′​=min{n,⌊3m/4⌋}, ℓJ=min⁡{⌊m/2⌋,⌈m−(m−nm′−1)m⌉−1}\ell_J=\min\{\lfloor m/2\rfloor,\lceil m-\sqrt{(m-n'_m-1)m}\rceil-1\}ℓJ​=min{⌊m/2⌋,⌈m−(m−nm′​−1)m​⌉−1}, error and failure targets m−2m^{-2}m−2, and appends zero coefficients. It approaches the endpoint parameters (μ,δ,λ)=(3/8,1/8,99/250)(\mu,\delta,\lambda)=(3/8,1/8,99/250)(μ,δ,λ)=(3/8,1/8,99/250) from the strict finite Johnson range, without asserting finite-length perfect satisfaction.

These conclusions turn the Sun–Wootters distributional improvement into efficient worst-case quantum optimization.

Formalization Note Theorem 7.1's printed “For each family member” is clarified to an eventual guarantee, matching its proof's positivity and decoder-feasibility bounds. This is an explicit proof-based scope clarification awaiting independent moderation. The finite exact identity is separate from the approximate universal-gate implementation. The paper's operator called inverse QFT has positive character and equals the frozen positive-sign QFT convention.

Correction to the printed source.

Printed: For each family member put ... and define Pu,m by equations (11) to (13) with largest active weight ell_m. Then ... there is a uniform bounded-error quantum algorithm.

Corrected: The finite target is defined on its positive-denominator and cutoff-at-least-three domain, and the sampling guarantees hold for every sufficiently large public parameter-family member.

Reason: Theorem 7.1 itself invokes the finite Johnson inequality and postselection estimate only for all sufficiently large m. Lemmas 3.2 and 6.4 are eventual, while equation (11) uses log log ell; early undefined targets cannot be normalized by total division.

Target

Theorem 1.1 (continues on PDF p.4); formal Theorem 7.1 and Corollaries 8.6, 8.8

Let ppp be prime, 1≤n<m≤p1\le n<m\le p1≤n<m≤p, and let α1,…,αm∈Fp\alpha_1,\ldots,\alpha_m\in\mathbb F_pα1​,…,αm​∈Fp​ be distinct public evaluation points. Every hidden set Si⊂FpS_i\subset\mathbb F_pSi​⊂Fp​ has the same known cardinality ccc, with 0<c<p0<c<p0<c<p. Put ρ=c/p\rho=c/pρ=c/p, Bij=αijB_{ij}=\alpha_i^jBij​=αij​ for j=0,…,n−1j=0,\ldots,n-1j=0,…,n−1, and H=BTH=B^{\mathsf T}H=BT. A coefficient vector x∈Fpnx\in\mathbb F_p^nx∈Fpn​ represents the polynomial Qx(T)=∑j=0n−1xjTjQ_x(T)=\sum_{j=0}^{n-1}x_jT^jQx​(T)=∑j=0n−1​xj​Tj; its satisfaction ratio is s(x)=m−1∣{i:Qx(αi)∈Si}∣s(x)=m^{-1}|\{i:Q_x(\alpha_i)\in S_i\}|s(x)=m−1∣{i:Qx​(αi​)∈Si​}∣. Access is through the indexed XOR oracle OS∣i,a,b⟩=∣i,a,b⊕1a∈Si⟩O_S|i,a,b\rangle=|i,a,b\oplus\mathbf1_{a\in S_i}\rangleOS​∣i,a,b⟩=∣i,a,b⊕1a∈Si​​⟩, with arbitrary full unitary behavior on invalid encodings.

For an integer cutoff 3≤ℓ≤m3\le\ell\le m3≤ℓ≤m, set σ=⌊log⁡log⁡ℓ⌋\sigma=\lfloor\log\log\ell\rfloorσ=⌊loglogℓ⌋, K={k∈{0,…,m}:ℓ−σ≤k≤ℓ}K=\{k\in\{0,\ldots,m\}:\ell-\sigma\le k\le\ell\}K={k∈{0,…,m}:ℓ−σ≤k≤ℓ}, and uk=(mk)−1/21k∈Ku_k=\binom mk^{-1/2}\mathbf1_{k\in K}uk​=(km​)−1/21k∈K​. Define gi(a)=(1a∈Si−ρ)/ρ(1−ρ)g_i(a)=(\mathbf1_{a\in S_i}-\rho)/\sqrt{\rho(1-\rho)}gi​(a)=(1a∈Si​​−ρ)/ρ(1−ρ)​, g^i(z)=p−1∑agi(a)e−2πiaz/p\widehat g_i(z)=p^{-1}\sum_a g_i(a)e^{-2\pi iaz/p}g​i​(z)=p−1∑a​gi​(a)e−2πiaz/p, qk(x)=∑∣T∣=k∏i∈Tgi((Bx)i)q_k(x)=\sum_{|T|=k}\prod_{i\in T}g_i((Bx)_i)qk​(x)=∑∣T∣=k​∏i∈T​gi​((Bx)i​) and F(x)=∑k∈Kukqk(x)F(x)=\sum_{k\in K}u_kq_k(x)F(x)=∑k∈K​uk​qk​(x). On its positive-denominator domain the Sun–Wootters law is

Pu(x)=∣F(x)∣2∑z∣F(z)∣2.P_u(x)=\frac{|F(x)|^2}{\sum_z|F(z)|^2}.Pu​(x)=∑z​∣F(z)∣2∣F(x)∣2​.

Write ay=uwt(y)∏i:yi≠0g^i(yi)a_y=u_{\mathrm{wt}(y)}\prod_{i:y_i\ne0}\widehat g_i(y_i)ay​=uwt(y)​∏i:yi​=0​g​i​(yi​), As=∑Hy=s, wt(y)∈KayA_s=\sum_{Hy=s,\,\mathrm{wt}(y)\in K}a_yAs​=∑Hy=s,wt(y)∈K​ay​, Z0=∑y∣ay∣2Z_0=\sum_y|a_y|^2Z0​=∑y​∣ay​∣2, and ZI=∑s∣As∣2Z_I=\sum_s|A_s|^2ZI​=∑s​∣As​∣2. Suppose Z0>0Z_0>0Z0​>0 and the target denominator is positive. For every complete duplicate-free canonical shell list, padded to the same L=2qL=2^qL=2q slots for every syndrome, the ideal attempt prepares Z0−1/2∑yay∣y,Hy⟩Z_0^{-1/2}\sum_y a_y|y,Hy\rangleZ0−1/2​∑y​ay​∣y,Hy⟩, reversibly indexes and erases the error, applies H⊗qH^{\otimes q}H⊗q to the index, and postselects (J,Q)=(0q,1)(J,Q)=(0^q,1)(J,Q)=(0q,1) using a match flag. It then applies the positive-character Fourier transform on the syndrome. Its success and conditional law satisfy

pideal=ZILZ0,L(x∣success)=Pu,ZI=p−n∑x∣F(x)∣2.p_{\rm ideal}=\frac{Z_I}{LZ_0},\qquad \mathcal L(x\mid\text{success})=P_u,\qquad Z_I=p^{-n}\sum_x|F(x)|^2.pideal​=LZ0​ZI​​,L(x∣success)=Pu​,ZI​=p−nx∑​∣F(x)∣2.

This finite identity preserves cancellation within fibers and asserts no running-time bound for an arbitrary unpriced list. For normalized ideal and implemented full-register states, ideal success at least 1/(2L)1/(2L)1/(2L), vector error at most min⁡{1/(8L),η/(42L)}\min\{1/(8L),\eta/(4\sqrt{2L})\}min{1/(8L),η/(42L​)}, and final Fourier operator error at most η/2\eta/2η/2, implemented success is at least 1/(4L)1/(4L)1/(4L) and conditional total variation error is at most η\etaη.

Now consider public parameter families with m→∞m\to\inftym→∞, n/m→r=2μ∈(0,1]n/m\to r=2\mu\in(0,1]n/m→r=2μ∈(0,1], and c/p→1/2c/p\to1/2c/p→1/2. Constants, programs and preprocessing are uniform over all sets of the promised cardinality and every supplied membership oracle. Let h(t)=−tlog⁡t−(1−t)log⁡(1−t)h(t)=-t\log t-(1-t)\log(1-t)h(t)=−tlogt−(1−t)log(1−t), using natural logarithms and 0log⁡0=00\log0=00log0=0, and define

E(μ,δ)=(μ+δ)h ⁣(μμ+δ)+(1−μ−δ)h ⁣(μ1−μ−δ)−h(2μ),E(\mu,\delta)=(\mu+\delta)h\!\left(\frac\mu{\mu+\delta}\right)+(1-\mu-\delta)h\!\left(\frac\mu{1-\mu-\delta}\right)-h(2\mu),E(μ,δ)=(μ+δ)h(μ+δμ​)+(1−μ−δ)h(1−μ−δμ​)−h(2μ), G(μ,λ)=(1−2μ)log⁡2+h(2μ)−(4μ−1)h ⁣(λ4μ−1)−(2−4μ)h ⁣(2μ−λ2−4μ)+λlog⁡(2/π).G(\mu,\lambda)=(1-2\mu)\log2+h(2\mu)-(4\mu-1)h\!\left(\frac\lambda{4\mu-1}\right)-(2-4\mu)h\!\left(\frac{2\mu-\lambda}{2-4\mu}\right)+\lambda\log(2/\pi).G(μ,λ)=(1−2μ)log2+h(2μ)−(4μ−1)h(4μ−1λ​)−(2−4μ)h(2−4μ2μ−λ​)+λlog(2/π).

All denominators in these ratios must be nonzero and all entropy arguments must belong to [0,1][0,1][0,1]. Fix 0<μ<1/20<\mu<1/20<μ<1/2, a positive rational δ≤1/2−μ\delta\le1/2-\muδ≤1/2−μ, and λ\lambdaλ in that domain with E+G<0E+G<0E+G<0 and μ+δ<1−1−2μ\mu+\delta<1-\sqrt{1-2\mu}μ+δ<1−1−2μ​. Put ℓm=min⁡{⌊n/2+δm⌋,⌊m/2⌋}\ell_m=\min\{\lfloor n/2+\delta m\rfloor,\lfloor m/2\rfloor\}ℓm​=min{⌊n/2+δm⌋,⌊m/2⌋}. Eventually the target is well defined, complete canonical lists admit one polynomial common padding length, and ideal success is at least 1/(2L)1/(2L)1/(2L). For every η,β∈(0,1/2)\eta,\beta\in(0,1/2)η,β∈(0,1/2), a uniform quantum algorithm with time polynomial in m,log⁡p,log⁡(1/η),log⁡(1/β)m,\log p,\log(1/\eta),\log(1/\beta)m,logp,log(1/η),log(1/β) satisfies

Pr⁡[x=⊥]≤β,TV⁡(L(x∣x≠⊥),Pu,m)≤η.\Pr[x=\bot]\le\beta,\qquad \operatorname{TV}(\mathcal L(x\mid x\ne\bot),P_{u,m})\le\eta.Pr[x=⊥]≤β,TV(L(x∣x=⊥),Pu,m​)≤η.

For every fixed default vector, the defaulted law has total variation distance at most η+β\eta+\betaη+β from Pu,mP_{u,m}Pu,m​ and expected score at least SCL1/2(μ+δ)−am−η−β\mathrm{SCL}_{1/2}(\mu+\delta)-a_m-\eta-\betaSCL1/2​(μ+δ)−am​−η−β, for some nonnegative am→0a_m\to0am​→0 independent of the hidden sets; here SCL1/2(t)=1/2+t(1−t)\mathrm{SCL}_{1/2}(t)=1/2+\sqrt{t(1-t)}SCL1/2​(t)=1/2+t(1−t)​ on [0,1/2][0,1/2][0,1/2]. Preprocessing, synthesized gates, queries, measurements, reversible/classical work, and capped restarts are counted.

The two balanced consequences are retained:

  1. For each fixed r∈[249/400,1)r\in[249/400,1)r∈[249/400,1), a gap γr>0\gamma_r>0γr​>0 and a uniform algorithm are chosen before the sets or parameter family. Eventually E[s(x)]≥SCL1/2(r/2)+γr\mathbb E[s(x)]\ge\mathrm{SCL}_{1/2}(r/2)+\gamma_rE[s(x)]≥SCL1/2​(r/2)+γr​. For every fixed ε>0\varepsilon>0ε>0 and β∈(0,1)\beta\in(0,1)β∈(0,1), polynomially many samples give s(x)≥SCL1/2(r/2)+γr−εs(x)\ge\mathrm{SCL}_{1/2}(r/2)+\gamma_r-\varepsilons(x)≥SCL1/2​(r/2)+γr​−ε with probability at least 1−β1-\beta1−β.
  2. For every limiting r∈[3/4,1]r\in[3/4,1]r∈[3/4,1], a uniform polynomial-time algorithm has nonnegative em,bm→0e_m,b_m\to0em​,bm​→0 with Pr⁡[s(x)≥1−em]≥1−bm\Pr[s(x)\ge1-e_m]\ge1-b_mPr[s(x)≥1−em​]≥1−bm​. Its construction uses nm′=min⁡{n,⌊3m/4⌋}n'_m=\min\{n,\lfloor3m/4\rfloor\}nm′​=min{n,⌊3m/4⌋}, ℓJ=min⁡{⌊m/2⌋,⌈m−(m−nm′−1)m⌉−1}\ell_J=\min\{\lfloor m/2\rfloor,\lceil m-\sqrt{(m-n'_m-1)m}\rceil-1\}ℓJ​=min{⌊m/2⌋,⌈m−(m−nm′​−1)m​⌉−1}, error and failure targets m−2m^{-2}m−2, and appends zero coefficients. It approaches the endpoint parameters (μ,δ,λ)=(3/8,1/8,99/250)(\mu,\delta,\lambda)=(3/8,1/8,99/250)(μ,δ,λ)=(3/8,1/8,99/250) from the strict finite Johnson range, without asserting finite-length perfect satisfaction.

These conclusions turn the Sun–Wootters distributional improvement into efficient worst-case quantum optimization.

Formalization Note Theorem 7.1's printed “For each family member” is clarified to an eventual guarantee, matching its proof's positivity and decoder-feasibility bounds. This is an explicit proof-based scope clarification awaiting independent moderation. The finite exact identity is separate from the approximate universal-gate implementation. The paper's operator called inverse QFT has positive character and equals the frozen positive-sign QFT convention.

Correction to the printed source.

Printed: For each family member put ... and define Pu,m by equations (11) to (13) with largest active weight ell_m. Then ... there is a uniform bounded-error quantum algorithm.

Corrected: The finite target is defined on its positive-denominator and cutoff-at-least-three domain, and the sampling guarantees hold for every sufficiently large public parameter-family member.

Reason: Theorem 7.1 itself invokes the finite Johnson inequality and postselection estimate only for all sufficiently large m. Lemmas 3.2 and 6.4 are eventual, while equation (11) uses log log ell; early undefined targets cannot be normalized by total division.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Efficient Exact Quantum Sampling from the Sun-Wootters Distribution for Optimal Polynomial Intersection, arXiv:2607.16541v2. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
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Quantum Information·Captain: Goku

Worst-Case Quantum Algorithm for Optimal Polynomial Intersection Beyond Decoded Quantum InterferometryResearch Paper

Motivation

Worst-Case Quantum Algorithm for Optimal Polynomial Intersection Beyond Decoded Quantum Interferometry establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Consider a growing public parameter family nj,kj,pj,ejn_j,k_j,p_j,e_jnj​,kj​,pj​,ej​, where pjp_jpj​ is prime, ej≥1e_j\ge1ej​≥1, nj,kj>0n_j,k_j>0nj​,kj​>0, nj/2≤kj≤nj≤qj=pjejn_j/2\le k_j\le n_j\le q_j=p_j^{e_j}nj​/2≤kj​≤nj​≤qj​=pjej​​, and nj,pj→∞n_j,p_j\to\inftynj​,pj​→∞. Put Rj=kj/njR_j=k_j/n_jRj​=kj​/nj​. Assume log⁡2qj≤Cnja\log_2 q_j\le Cn_j^alog2​qj​≤Cnja​ eventually for fixed C>0C>0C>0 and a∈Na\in\mathbb Na∈N. Each Fqj\mathbb F_{q_j}Fqj​​ has its standard effective polynomial-basis binary representation, specified by its characteristic, extension degree and irreducible modulus. Fix a target sss and assume one of these two eventual regimes, with a common fixed margin c>0c>0c>0:

  1. s=1s=1s=1 and Rj≥3/4+cR_j\ge3/4+cRj​≥3/4+c.
  2. 1/2<s<11/2<s<11/2<s<1, Rj≤3/4R_j\le3/4Rj​≤3/4, and
Rj≥1−(s/2+(1−s)/2)4+c,H2(Rj)+Rjlog⁡2(3(2s−13)1/(1−Rj))≤−c.R_j\ge1-\left(\sqrt{s/2}+\sqrt{(1-s)/2}\right)^4+c,\qquad H_2(R_j)+R_j\log_2\left(3\left(\frac{2s-1}{\sqrt3}\right)^{1/(1-R_j)}\right)\le-c.Rj​≥1−(s/2​+(1−s)/2​)4+c,H2​(Rj​)+Rj​log2​(3(3​2s−1​)1/(1−Rj​))≤−c.

Here H2(t)=−tlog⁡2t−(1−t)log⁡2(1−t)H_2(t)=-t\log_2t-(1-t)\log_2(1-t)H2​(t)=−tlog2​t−(1−t)log2​(1−t), with 0log⁡20=00\log_20=00log2​0=0.

Let β:N→[0,∞)\beta:\mathbb N\to[0,\infty)β:N→[0,∞) tend to zero. There exist a uniform quantum oracle solver, a polynomial www and an index j0j_0j0​ such that, for every j≥j0j\ge j_0j≥j0​, every tuple of distinct evaluation points α1,…,αnj∈Fqj\alpha_1,\ldots,\alpha_{n_j}\in\mathbb F_{q_j}α1​,…,αnj​​∈Fqj​​, and every hidden subset family satisfying

max⁡i∣∣Si∣qj−12∣≤β(nj),\max_i\left|\frac{|S_i|}{q_j}-\frac12\right|\le\beta(n_j),imax​​qj​∣Si​∣​−21​​≤β(nj​),

the solver outputs a polynomial P∈Fqj[X]P\in\mathbb F_{q_j}[X]P∈Fqj​​[X] for which

Pr⁡ ⁣[deg⁡P<kj and ∣{i:P(αi)∈Si}∣≥snj]≥23,work⁡≤w(nj).\Pr\!\left[\deg P<k_j\ \text{and}\ |\{i:P(\alpha_i)\in S_i\}|\ge s n_j\right]\ge\frac23, \qquad \operatorname{work}\le w(n_j).Pr[degP<kj​ and ∣{i:P(αi​)∈Si​}∣≥snj​]≥32​,work≤w(nj​).

Its classical constructor receives only the public field description, nj,kjn_j,k_jnj​,kj​, the evaluation points and the integer target ⌈snj⌉\lceil s n_j\rceil⌈snj​⌉. The sets are accessed through their individual quantum XOR membership oracles. Work counts queries, standard Clifford+T gates, measurements, preparations, classical control, workspace and coefficient decoding; constructor time and space are polynomial in nj+log⁡qjn_j+\log q_jnj​+logqj​. The constants and threshold are uniform over evaluation points and hidden sets, and probability refers to internal coins and measurements.

This gives an algorithm on every promised instance, including exact perfect satisfaction in the first branch. No random-instance assumption, efficient-decoder hypothesis, or pre-existing-solution hypothesis is imposed.

Formalization Note The asymptotic reading makes the log⁡q\log qlogq bound and high-rate constant margin explicit using Theorem 6.1 and Remark 6.2. The printed informal high-rate sentence omits them. Unequal densities are retained under footnote 3. Rates tending to one and Rj=1R_j=1Rj​=1 are retained through constructive dimension reduction. These bridges require independent mathematical moderation.

Target

Theorem 1.1 (continues on PDF p.5)

Consider a growing public parameter family nj,kj,pj,ejn_j,k_j,p_j,e_jnj​,kj​,pj​,ej​, where pjp_jpj​ is prime, ej≥1e_j\ge1ej​≥1, nj,kj>0n_j,k_j>0nj​,kj​>0, nj/2≤kj≤nj≤qj=pjejn_j/2\le k_j\le n_j\le q_j=p_j^{e_j}nj​/2≤kj​≤nj​≤qj​=pjej​​, and nj,pj→∞n_j,p_j\to\inftynj​,pj​→∞. Put Rj=kj/njR_j=k_j/n_jRj​=kj​/nj​. Assume log⁡2qj≤Cnja\log_2 q_j\le Cn_j^alog2​qj​≤Cnja​ eventually for fixed C>0C>0C>0 and a∈Na\in\mathbb Na∈N. Each Fqj\mathbb F_{q_j}Fqj​​ has its standard effective polynomial-basis binary representation, specified by its characteristic, extension degree and irreducible modulus. Fix a target sss and assume one of these two eventual regimes, with a common fixed margin c>0c>0c>0:

  1. s=1s=1s=1 and Rj≥3/4+cR_j\ge3/4+cRj​≥3/4+c.
  2. 1/2<s<11/2<s<11/2<s<1, Rj≤3/4R_j\le3/4Rj​≤3/4, and
Rj≥1−(s/2+(1−s)/2)4+c,H2(Rj)+Rjlog⁡2(3(2s−13)1/(1−Rj))≤−c.R_j\ge1-\left(\sqrt{s/2}+\sqrt{(1-s)/2}\right)^4+c,\qquad H_2(R_j)+R_j\log_2\left(3\left(\frac{2s-1}{\sqrt3}\right)^{1/(1-R_j)}\right)\le-c.Rj​≥1−(s/2​+(1−s)/2​)4+c,H2​(Rj​)+Rj​log2​(3(3​2s−1​)1/(1−Rj​))≤−c.

Here H2(t)=−tlog⁡2t−(1−t)log⁡2(1−t)H_2(t)=-t\log_2t-(1-t)\log_2(1-t)H2​(t)=−tlog2​t−(1−t)log2​(1−t), with 0log⁡20=00\log_20=00log2​0=0.

Let β:N→[0,∞)\beta:\mathbb N\to[0,\infty)β:N→[0,∞) tend to zero. There exist a uniform quantum oracle solver, a polynomial www and an index j0j_0j0​ such that, for every j≥j0j\ge j_0j≥j0​, every tuple of distinct evaluation points α1,…,αnj∈Fqj\alpha_1,\ldots,\alpha_{n_j}\in\mathbb F_{q_j}α1​,…,αnj​​∈Fqj​​, and every hidden subset family satisfying

max⁡i∣∣Si∣qj−12∣≤β(nj),\max_i\left|\frac{|S_i|}{q_j}-\frac12\right|\le\beta(n_j),imax​​qj​∣Si​∣​−21​​≤β(nj​),

the solver outputs a polynomial P∈Fqj[X]P\in\mathbb F_{q_j}[X]P∈Fqj​​[X] for which

Pr⁡ ⁣[deg⁡P<kj and ∣{i:P(αi)∈Si}∣≥snj]≥23,work⁡≤w(nj).\Pr\!\left[\deg P<k_j\ \text{and}\ |\{i:P(\alpha_i)\in S_i\}|\ge s n_j\right]\ge\frac23, \qquad \operatorname{work}\le w(n_j).Pr[degP<kj​ and ∣{i:P(αi​)∈Si​}∣≥snj​]≥32​,work≤w(nj​).

Its classical constructor receives only the public field description, nj,kjn_j,k_jnj​,kj​, the evaluation points and the integer target ⌈snj⌉\lceil s n_j\rceil⌈snj​⌉. The sets are accessed through their individual quantum XOR membership oracles. Work counts queries, standard Clifford+T gates, measurements, preparations, classical control, workspace and coefficient decoding; constructor time and space are polynomial in nj+log⁡qjn_j+\log q_jnj​+logqj​. The constants and threshold are uniform over evaluation points and hidden sets, and probability refers to internal coins and measurements.

This gives an algorithm on every promised instance, including exact perfect satisfaction in the first branch. No random-instance assumption, efficient-decoder hypothesis, or pre-existing-solution hypothesis is imposed.

Formalization Note The asymptotic reading makes the log⁡q\log qlogq bound and high-rate constant margin explicit using Theorem 6.1 and Remark 6.2. The printed informal high-rate sentence omits them. Unequal densities are retained under footnote 3. Rates tending to one and Rj=1R_j=1Rj​=1 are retained through constructive dimension reduction. These bridges require independent mathematical moderation.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Worst-Case Quantum Algorithm for Optimal Polynomial Intersection Beyond Decoded Quantum Interferometry, arXiv:2607.14650v1. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Information·Captain: Goku

Hamiltonian Decoded Quantum Interferometry for General Pauli HamiltoniansResearch Paper

Motivation

Hamiltonian Decoded Quantum Interferometry for General Pauli Hamiltonians establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let n,m≥1n,m\ge 1n,m≥1 and ℓ≥0\ell\ge 0ℓ≥0 be integers. Let H=∑i=1mciPiH=\sum_{i=1}^{m}c_iP_iH=∑i=1m​ci​Pi​ be a classically known Hamiltonian on nnn qubits, where ci∈Rc_i\in\mathbb Rci​∈R and the PiP_iPi​ are distinct canonical Hermitian Pauli operators that commute pairwise. Let P(x)=∑j=0ℓajxjP(x)=\sum_{j=0}^{\ell}a_jx^jP(x)=∑j=0ℓ​aj​xj be a real polynomial of degree exactly ℓ\ellℓ, and assume P(H)≠0P(H)\ne 0P(H)=0. Write B⊤∈F22n×mB^\top\in\mathbb F_2^{2n\times m}B⊤∈F22n×m​ for the matrix whose columns are the symplectic labels of the PiP_iPi​, with the ZZZ coordinates preceding the XXX coordinates. Assume there exists a unitary decoder DDD on the mmm-qubit label register and the 2n2n2n-qubit syndrome register satisfying

D∣y⟩∣B⊤y⟩=∣0⟩∣B⊤y⟩(1≤∣y∣≤ℓ),w0≠0 ⟹ D∣0⟩∣0⟩=∣0⟩∣0⟩.D|y\rangle|B^\top y\rangle=|0\rangle|B^\top y\rangle\quad(1\le |y|\le\ell), \qquad w_0\ne0\ \Longrightarrow\ D|0\rangle|0\rangle=|0\rangle|0\rangle.D∣y⟩∣B⊤y⟩=∣0⟩∣B⊤y⟩(1≤∣y∣≤ℓ),w0​=0 ⟹ D∣0⟩∣0⟩=∣0⟩∣0⟩.

Here ∣y∣|y|∣y∣ is Hamming weight and w0w_0w0​ is the zero-string reference coefficient defined below. The zero-branch guarantee is required only when w0≠0w_0\ne0w0​=0; when w0=0w_0=0w0​=0, that decoder input is unrestricted. All other decoder inputs are unrestricted.

There is an exact quantum preparation circuit, chosen from the known Hamiltonian and polynomial before choosing the decoder, that works for every decoder with these guarantees and prepares

ρP(H)=P(H)2Tr⁡[P(H)2].\rho_P(H)=\frac{P(H)^2}{\operatorname{Tr}[P(H)^2]}.ρP​(H)=Tr[P(H)2]P(H)2​.

It starts with zeroed registers, uses exactly one plain forward application of DDD, and uses no adjoint or controlled decoder calls. The output is the reduced density matrix after discarding the other registers, with no postselection or success-probability qualification.

For clarity, define the real reference coefficients and their normalization by

wy=∑j=0ℓajj!∑μ∈Z≥0m∣μ∣=j, μ≡y(mod2)∏i=1mciμi∏i=1mμi!,N=∑y∈{0,1}mwy2.w_y=\sum_{j=0}^{\ell}a_jj! \sum_{\substack{\mu\in\mathbb Z_{\ge0}^{m}\\|\mu|=j,\ \mu\equiv y\pmod2}} \frac{\prod_{i=1}^{m}c_i^{\mu_i}}{\prod_{i=1}^{m}\mu_i!}, \qquad \mathcal N=\sqrt{\sum_{y\in\{0,1\}^{m}}w_y^2}.wy​=j=0∑ℓ​aj​j!μ∈Z≥0m​∣μ∣=j, μ≡y(mod2)​∑​∏i=1m​μi​!∏i=1m​ciμi​​​,N=y∈{0,1}m∑​wy2​​.

The reference ∣R⟩=N−1∑ywy∣y⟩|R\rangle=\mathcal N^{-1}\sum_yw_y|y\rangle∣R⟩=N−1∑y​wy​∣y⟩ is constructed by the algorithm, rather than supplied as input. In particular,

N>0,N2=Tr⁡[P(H)2]2n,∣ϕ⟩=N−1(P(H)⊗I)∣Φn⟩,Tr⁡C∣ϕ⟩⟨ϕ∣=ρP(H),\mathcal N>0,\qquad \mathcal N^2=\frac{\operatorname{Tr}[P(H)^2]}{2^n},\qquad |\phi\rangle=\mathcal N^{-1}(P(H)\otimes I)|\Phi_n\rangle,\qquad \operatorname{Tr}_{C}|\phi\rangle\langle\phi|=\rho_P(H),N>0,N2=2nTr[P(H)2]​,∣ϕ⟩=N−1(P(H)⊗I)∣Φn​⟩,TrC​∣ϕ⟩⟨ϕ∣=ρP​(H),

where ∣Φn⟩=2−n/2∑z∣z⟩B∣z⟩C|\Phi_n\rangle=2^{-n/2}\sum_z|z\rangle_B|z\rangle_C∣Φn​⟩=2−n/2∑z​∣z⟩B​∣z⟩C​; both ∣R⟩|R\rangle∣R⟩ and ∣ϕ⟩|\phi\rangle∣ϕ⟩ have unit norm.

The circuit includes a concrete classical arithmetic program that computes N\mathcal NN and all boundary and local-matrix entries of the reference MPS from the coefficients alone. It may introduce only the numeric constants 0,1,−10,1,-10,1,−1, and the entries of its quantum gates are obtained from that program's results. There exist an absolute C>0C>0C>0, a polynomial qqq with nonnegative integer coefficients, and thresholds ℓ0≥1\ell_0\ge1ℓ0​≥1 and s0s_0s0​, all independent of sizes, Pauli terms, coefficients, and decoder, such that

Tclassical≤Cmℓ3(ℓ≥ℓ0),Tquantum≤Cmq(ℓ+n)(ℓ+n≥s0).T_{\rm classical}\le C m\ell^3\quad(\ell\ge\ell_0),\qquad T_{\rm quantum}\le C m q(\ell+n)\quad(\ell+n\ge s_0).Tclassical​≤Cmℓ3(ℓ≥ℓ0​),Tquantum​≤Cmq(ℓ+n)(ℓ+n≥s0​).

Here classical cost counts actual arithmetic and memory instructions, and quantum cost counts the circuit's gate and oracle steps plus initialization of its qubits. This is the paper's ideal model with unit-cost real arithmetic and exact arbitrary one- and two-qubit unitary gates.

This result supplies an exact polynomial-filtered density matrix using a perfect decoder even for general real commuting Pauli coefficients, without assuming the reference state has already been prepared.

Formalization Note. The proof's j=0,…,ℓj=0,\ldots,\ellj=0,…,ℓ convention replaces the theorem display's j=1,…,ℓj=1,\ldots,\ellj=1,…,ℓ. Real polynomial coefficients, the nonzero condition, and the decoder's zero-branch guarantee for an occupied reference branch are explicit corrections needed for normalization and coherence. The conditional zero-branch guarantee strengthens literal Eq. (7) only when w0≠0w_0\ne0w0​=0 and is not inferred from it. Pauli-product phases are retained through the Bell basis change and its inverse. The ordinary positive-n,mn,mn,m regime is explicit; nonzero constant polynomials are included, and asymptotic bounds are applied only above their stated thresholds.

Correction to the printed source.

Printed: Theorem 5 displays j=1,...,l, does not explicitly type a_j or exclude P(H)=0, and refers to Eq.(7), which specifies decoder action only for 1<=|y|<=l. The proof suppresses Pauli-product phases in its Bell-basis display.

Corrected: Use the proof convention j=0,...,l with real polynomial coefficients; require P(H)!=0; retain Eq.(7) and require D|0,0>=|0,0> only if the Eq.(10) coefficient w_0 is nonzero. Preserve product phases under the coherent Bell transform and its inverse.

Reason: The proof and MPS boundaries include a_0. Real coefficients and P(H)!=0 make P(H)^2/Tr[P(H)^2] a density matrix. Eq.(7) leaves an occupied zero branch uncontrolled; fixing only that occupied branch restores coherent erasure without excluding H=I,P=x, whose w_0 vanishes and whose positive-weight decoder necessarily moves |0,0>. A linear Bell transform must preserve Pauli-product signs.

Target

Theorem 5, §3 (proof continues on PDF p.9)

Let n,m≥1n,m\ge 1n,m≥1 and ℓ≥0\ell\ge 0ℓ≥0 be integers. Let H=∑i=1mciPiH=\sum_{i=1}^{m}c_iP_iH=∑i=1m​ci​Pi​ be a classically known Hamiltonian on nnn qubits, where ci∈Rc_i\in\mathbb Rci​∈R and the PiP_iPi​ are distinct canonical Hermitian Pauli operators that commute pairwise. Let P(x)=∑j=0ℓajxjP(x)=\sum_{j=0}^{\ell}a_jx^jP(x)=∑j=0ℓ​aj​xj be a real polynomial of degree exactly ℓ\ellℓ, and assume P(H)≠0P(H)\ne 0P(H)=0. Write B⊤∈F22n×mB^\top\in\mathbb F_2^{2n\times m}B⊤∈F22n×m​ for the matrix whose columns are the symplectic labels of the PiP_iPi​, with the ZZZ coordinates preceding the XXX coordinates. Assume there exists a unitary decoder DDD on the mmm-qubit label register and the 2n2n2n-qubit syndrome register satisfying

D∣y⟩∣B⊤y⟩=∣0⟩∣B⊤y⟩(1≤∣y∣≤ℓ),w0≠0 ⟹ D∣0⟩∣0⟩=∣0⟩∣0⟩.D|y\rangle|B^\top y\rangle=|0\rangle|B^\top y\rangle\quad(1\le |y|\le\ell), \qquad w_0\ne0\ \Longrightarrow\ D|0\rangle|0\rangle=|0\rangle|0\rangle.D∣y⟩∣B⊤y⟩=∣0⟩∣B⊤y⟩(1≤∣y∣≤ℓ),w0​=0 ⟹ D∣0⟩∣0⟩=∣0⟩∣0⟩.

Here ∣y∣|y|∣y∣ is Hamming weight and w0w_0w0​ is the zero-string reference coefficient defined below. The zero-branch guarantee is required only when w0≠0w_0\ne0w0​=0; when w0=0w_0=0w0​=0, that decoder input is unrestricted. All other decoder inputs are unrestricted.

There is an exact quantum preparation circuit, chosen from the known Hamiltonian and polynomial before choosing the decoder, that works for every decoder with these guarantees and prepares

ρP(H)=P(H)2Tr⁡[P(H)2].\rho_P(H)=\frac{P(H)^2}{\operatorname{Tr}[P(H)^2]}.ρP​(H)=Tr[P(H)2]P(H)2​.

It starts with zeroed registers, uses exactly one plain forward application of DDD, and uses no adjoint or controlled decoder calls. The output is the reduced density matrix after discarding the other registers, with no postselection or success-probability qualification.

For clarity, define the real reference coefficients and their normalization by

wy=∑j=0ℓajj!∑μ∈Z≥0m∣μ∣=j, μ≡y(mod2)∏i=1mciμi∏i=1mμi!,N=∑y∈{0,1}mwy2.w_y=\sum_{j=0}^{\ell}a_jj! \sum_{\substack{\mu\in\mathbb Z_{\ge0}^{m}\\|\mu|=j,\ \mu\equiv y\pmod2}} \frac{\prod_{i=1}^{m}c_i^{\mu_i}}{\prod_{i=1}^{m}\mu_i!}, \qquad \mathcal N=\sqrt{\sum_{y\in\{0,1\}^{m}}w_y^2}.wy​=j=0∑ℓ​aj​j!μ∈Z≥0m​∣μ∣=j, μ≡y(mod2)​∑​∏i=1m​μi​!∏i=1m​ciμi​​​,N=y∈{0,1}m∑​wy2​​.

The reference ∣R⟩=N−1∑ywy∣y⟩|R\rangle=\mathcal N^{-1}\sum_yw_y|y\rangle∣R⟩=N−1∑y​wy​∣y⟩ is constructed by the algorithm, rather than supplied as input. In particular,

N>0,N2=Tr⁡[P(H)2]2n,∣ϕ⟩=N−1(P(H)⊗I)∣Φn⟩,Tr⁡C∣ϕ⟩⟨ϕ∣=ρP(H),\mathcal N>0,\qquad \mathcal N^2=\frac{\operatorname{Tr}[P(H)^2]}{2^n},\qquad |\phi\rangle=\mathcal N^{-1}(P(H)\otimes I)|\Phi_n\rangle,\qquad \operatorname{Tr}_{C}|\phi\rangle\langle\phi|=\rho_P(H),N>0,N2=2nTr[P(H)2]​,∣ϕ⟩=N−1(P(H)⊗I)∣Φn​⟩,TrC​∣ϕ⟩⟨ϕ∣=ρP​(H),

where ∣Φn⟩=2−n/2∑z∣z⟩B∣z⟩C|\Phi_n\rangle=2^{-n/2}\sum_z|z\rangle_B|z\rangle_C∣Φn​⟩=2−n/2∑z​∣z⟩B​∣z⟩C​; both ∣R⟩|R\rangle∣R⟩ and ∣ϕ⟩|\phi\rangle∣ϕ⟩ have unit norm.

The circuit includes a concrete classical arithmetic program that computes N\mathcal NN and all boundary and local-matrix entries of the reference MPS from the coefficients alone. It may introduce only the numeric constants 0,1,−10,1,-10,1,−1, and the entries of its quantum gates are obtained from that program's results. There exist an absolute C>0C>0C>0, a polynomial qqq with nonnegative integer coefficients, and thresholds ℓ0≥1\ell_0\ge1ℓ0​≥1 and s0s_0s0​, all independent of sizes, Pauli terms, coefficients, and decoder, such that

Tclassical≤Cmℓ3(ℓ≥ℓ0),Tquantum≤Cmq(ℓ+n)(ℓ+n≥s0).T_{\rm classical}\le C m\ell^3\quad(\ell\ge\ell_0),\qquad T_{\rm quantum}\le C m q(\ell+n)\quad(\ell+n\ge s_0).Tclassical​≤Cmℓ3(ℓ≥ℓ0​),Tquantum​≤Cmq(ℓ+n)(ℓ+n≥s0​).

Here classical cost counts actual arithmetic and memory instructions, and quantum cost counts the circuit's gate and oracle steps plus initialization of its qubits. This is the paper's ideal model with unit-cost real arithmetic and exact arbitrary one- and two-qubit unitary gates.

This result supplies an exact polynomial-filtered density matrix using a perfect decoder even for general real commuting Pauli coefficients, without assuming the reference state has already been prepared.

Formalization Note. The proof's j=0,…,ℓj=0,\ldots,\ellj=0,…,ℓ convention replaces the theorem display's j=1,…,ℓj=1,\ldots,\ellj=1,…,ℓ. Real polynomial coefficients, the nonzero condition, and the decoder's zero-branch guarantee for an occupied reference branch are explicit corrections needed for normalization and coherence. The conditional zero-branch guarantee strengthens literal Eq. (7) only when w0≠0w_0\ne0w0​=0 and is not inferred from it. Pauli-product phases are retained through the Bell basis change and its inverse. The ordinary positive-n,mn,mn,m regime is explicit; nonzero constant polynomials are included, and asymptotic bounds are applied only above their stated thresholds.

Correction to the printed source.

Printed: Theorem 5 displays j=1,...,l, does not explicitly type a_j or exclude P(H)=0, and refers to Eq.(7), which specifies decoder action only for 1<=|y|<=l. The proof suppresses Pauli-product phases in its Bell-basis display.

Corrected: Use the proof convention j=0,...,l with real polynomial coefficients; require P(H)!=0; retain Eq.(7) and require D|0,0>=|0,0> only if the Eq.(10) coefficient w_0 is nonzero. Preserve product phases under the coherent Bell transform and its inverse.

Reason: The proof and MPS boundaries include a_0. Real coefficients and P(H)!=0 make P(H)^2/Tr[P(H)^2] a density matrix. Eq.(7) leaves an occupied zero branch uncontrolled; fixing only that occupied branch restores coherent erasure without excluding H=I,P=x, whose w_0 vanishes and whose positive-weight decoder necessarily moves |0,0>. A linear Bell transform must preserve Pauli-product signs.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Hamiltonian Decoded Quantum Interferometry for General Pauli Hamiltonians, arXiv:2601.18773v1. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Information·Captain: Goku

Multivariate Decoded Quantum Interferometry for Weighted OptimizationResearch Paper

Motivation

Multivariate Decoded Quantum Interferometry for Weighted Optimization establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let ppp be prime and 1≤r<p1\le r<p1≤r<p. Let B∈Fpm×nB\in\mathbb F_p^{m\times n}B∈Fpm×n​ with m>0m>0m>0, and let Li⊆FpL_i\subseteq\mathbb F_pLi​⊆Fp​ have cardinality rrr. Define fi(y)=1f_i(y)=1fi​(y)=1 on LiL_iLi​ and fi(y)=−1f_i(y)=-1fi​(y)=−1 otherwise. Partition [m][m][m] into nonempty blocks S1,…,SNS_1,\ldots,S_NS1​,…,SN​, write mt=∣St∣m_t=|S_t|mt​=∣St​∣, and assign positive weights gtg_tgt​. Put Ft(x)=∑i∈Stfi(bi⋅x)F_t(x)=\sum_{i\in S_t}f_i(b_i\cdot x)Ft​(x)=∑i∈St​​fi​(bi​⋅x) and Fg(x)=∑tgtFt(x)F_g(x)=\sum_t g_tF_t(x)Fg​(x)=∑t​gt​Ft​(x), where bib_ibi​ is row iii of BBB and x∈Fpnx\in\mathbb F_p^nx∈Fpn​.

Fix an exact degree ratio μ=ℓ/m∈(0,1/2)\mu=\ell/m\in(0,1/2)μ=ℓ/m∈(0,1/2), with integer ℓ\ellℓ, and assume 2ℓ+1<d⊥2\ell+1<d^\perp2ℓ+1<d⊥, where d⊥d^\perpd⊥ is the minimum nonzero Hamming weight in ker⁡B⊤\ker B^\topkerB⊤ (infinite when this kernel is zero). Let EoptE_{\mathrm{opt}}Eopt​ be the supremum of ∑x∣ψP(x)∣2Fg(x)\sum_x|\psi_P(x)|^2F_g(x)∑x​∣ψP​(x)∣2Fg​(x) over complex multivariate polynomials of total degree at most ℓ\ellℓ such that ψP(x)=P(F1(x),…,FN(x))\psi_P(x)=P(F_1(x),\ldots,F_N(x))ψP​(x)=P(F1​(x),…,FN​(x)) has unit norm. This supremum is attained by an admissible polynomial.

Write fˉ=2r/p−1\bar f=2r/p-1fˉ​=2r/p−1, σ=2r(p−r)/p\sigma=2\sqrt{r(p-r)}/pσ=2r(p−r)​/p, κ=(p−2r)/r(p−r)\kappa=(p-2r)/\sqrt{r(p-r)}κ=(p−2r)/r(p−r)​, and define

Γg,m,κ(μ)=sup⁡0≤αt≤1 (1≤t≤N)∑t(mt/m)αt≤μ∑tmtmgt(καt+2αt(1−αt)).\Gamma_{g,m,\kappa}(\mu)=\sup_{\substack{0\le\alpha_t\le1\ (1\le t\le N)\\\sum_t(m_t/m)\alpha_t\le\mu}}\sum_t\frac{m_t}{m}g_t\left(\kappa\alpha_t+2\sqrt{\alpha_t(1-\alpha_t)}\right).Γg,m,κ​(μ)=0≤αt​≤1 (1≤t≤N)∑t​(mt​/m)αt​≤μ​sup​t∑​mmt​​gt​(καt​+2αt​(1−αt​)​).

For each fixed κ\kappaκ, there are Cκ>0C_\kappa>0Cκ​>0 and an integer m0m_0m0​, chosen before all other instance data and μ\muμ, such that every admissible instance with m≥m0m\ge m_0m≥m0​ satisfies

Eoptm=fˉ∑tgtmtm+σΓg,m,κ(μ)+R,∣R∣≤Cκm∑tgtmt3/4.\frac{E_{\mathrm{opt}}}{m}=\bar f\sum_t\frac{g_tm_t}{m}+\sigma\Gamma_{g,m,\kappa}(\mu)+R, \qquad |R|\le\frac{C_\kappa}{m}\sum_tg_tm_t^{3/4}.mEopt​​=fˉ​t∑​mgt​mt​​+σΓg,m,κ​(μ)+R,∣R∣≤mCκ​​t∑​gt​mt3/4​.

Along any admissible family with fixed κ,μ,N\kappa,\mu,Nκ,μ,N, unbounded mmm, and eventually bounded max⁡tgt\max_tg_tmaxt​gt​, the residual RRR tends to zero. No convergence of block proportions is required.

This characterizes the asymptotically optimal signed weighted objective among multivariate DQI states. It does not impose decoder access or a preparation complexity bound.

Formalization Note The range 1≤r<p1\le r<p1≤r<p is explicitly recalled by Appendix A (PDF p.30) and is carried as a standing assumption although omitted from the printed theorem sentence. Exact integer pairs (ℓ,m)(\ell,m)(ℓ,m) are used; no rounding convention is added.

Target

Theorem 2 (Asymptotically Optimal Expectation Value), equations (9)–(10)

Let ppp be prime and 1≤r<p1\le r<p1≤r<p. Let B∈Fpm×nB\in\mathbb F_p^{m\times n}B∈Fpm×n​ with m>0m>0m>0, and let Li⊆FpL_i\subseteq\mathbb F_pLi​⊆Fp​ have cardinality rrr. Define fi(y)=1f_i(y)=1fi​(y)=1 on LiL_iLi​ and fi(y)=−1f_i(y)=-1fi​(y)=−1 otherwise. Partition [m][m][m] into nonempty blocks S1,…,SNS_1,\ldots,S_NS1​,…,SN​, write mt=∣St∣m_t=|S_t|mt​=∣St​∣, and assign positive weights gtg_tgt​. Put Ft(x)=∑i∈Stfi(bi⋅x)F_t(x)=\sum_{i\in S_t}f_i(b_i\cdot x)Ft​(x)=∑i∈St​​fi​(bi​⋅x) and Fg(x)=∑tgtFt(x)F_g(x)=\sum_t g_tF_t(x)Fg​(x)=∑t​gt​Ft​(x), where bib_ibi​ is row iii of BBB and x∈Fpnx\in\mathbb F_p^nx∈Fpn​.

Fix an exact degree ratio μ=ℓ/m∈(0,1/2)\mu=\ell/m\in(0,1/2)μ=ℓ/m∈(0,1/2), with integer ℓ\ellℓ, and assume 2ℓ+1<d⊥2\ell+1<d^\perp2ℓ+1<d⊥, where d⊥d^\perpd⊥ is the minimum nonzero Hamming weight in ker⁡B⊤\ker B^\topkerB⊤ (infinite when this kernel is zero). Let EoptE_{\mathrm{opt}}Eopt​ be the supremum of ∑x∣ψP(x)∣2Fg(x)\sum_x|\psi_P(x)|^2F_g(x)∑x​∣ψP​(x)∣2Fg​(x) over complex multivariate polynomials of total degree at most ℓ\ellℓ such that ψP(x)=P(F1(x),…,FN(x))\psi_P(x)=P(F_1(x),\ldots,F_N(x))ψP​(x)=P(F1​(x),…,FN​(x)) has unit norm. This supremum is attained by an admissible polynomial.

Write fˉ=2r/p−1\bar f=2r/p-1fˉ​=2r/p−1, σ=2r(p−r)/p\sigma=2\sqrt{r(p-r)}/pσ=2r(p−r)​/p, κ=(p−2r)/r(p−r)\kappa=(p-2r)/\sqrt{r(p-r)}κ=(p−2r)/r(p−r)​, and define

Γg,m,κ(μ)=sup⁡0≤αt≤1 (1≤t≤N)∑t(mt/m)αt≤μ∑tmtmgt(καt+2αt(1−αt)).\Gamma_{g,m,\kappa}(\mu)=\sup_{\substack{0\le\alpha_t\le1\ (1\le t\le N)\\\sum_t(m_t/m)\alpha_t\le\mu}}\sum_t\frac{m_t}{m}g_t\left(\kappa\alpha_t+2\sqrt{\alpha_t(1-\alpha_t)}\right).Γg,m,κ​(μ)=0≤αt​≤1 (1≤t≤N)∑t​(mt​/m)αt​≤μ​sup​t∑​mmt​​gt​(καt​+2αt​(1−αt​)​).

For each fixed κ\kappaκ, there are Cκ>0C_\kappa>0Cκ​>0 and an integer m0m_0m0​, chosen before all other instance data and μ\muμ, such that every admissible instance with m≥m0m\ge m_0m≥m0​ satisfies

Eoptm=fˉ∑tgtmtm+σΓg,m,κ(μ)+R,∣R∣≤Cκm∑tgtmt3/4.\frac{E_{\mathrm{opt}}}{m}=\bar f\sum_t\frac{g_tm_t}{m}+\sigma\Gamma_{g,m,\kappa}(\mu)+R, \qquad |R|\le\frac{C_\kappa}{m}\sum_tg_tm_t^{3/4}.mEopt​​=fˉ​t∑​mgt​mt​​+σΓg,m,κ​(μ)+R,∣R∣≤mCκ​​t∑​gt​mt3/4​.

Along any admissible family with fixed κ,μ,N\kappa,\mu,Nκ,μ,N, unbounded mmm, and eventually bounded max⁡tgt\max_tg_tmaxt​gt​, the residual RRR tends to zero. No convergence of block proportions is required.

This characterizes the asymptotically optimal signed weighted objective among multivariate DQI states. It does not impose decoder access or a preparation complexity bound.

Formalization Note The range 1≤r<p1\le r<p1≤r<p is explicitly recalled by Appendix A (PDF p.30) and is carried as a standing assumption although omitted from the printed theorem sentence. Exact integer pairs (ℓ,m)(\ell,m)(ℓ,m) are used; no rounding convention is added.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Multivariate Decoded Quantum Interferometry for Weighted Optimization, arXiv:2605.10666v2. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
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OptimizationQuantum Information·Captain: Goku

Randomized and quantum approximate matrix multiplicationResearch Paper

Motivation

Randomized and quantum approximate matrix multiplication establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Fix a classical exact-arithmetic matrix multiplication implementation with achievable exponent ω≥2\omega\ge 2ω≥2. Let n≥1n\ge1n≥1, K≥1K\ge1K≥1, and let A1,…,AK∈Rn×nA_1,\ldots,A_K\in\mathbb R^{n\times n}A1​,…,AK​∈Rn×n be arbitrary matrices. Write F=∏j=1K∥Aj∥FF=\prod_{j=1}^K\|A_j\|_FF=∏j=1K​∥Aj​∥F​, where ∥A∥F=(∑i,jAij2)1/2\|A\|_F=(\sum_{i,j}A_{ij}^2)^{1/2}∥A∥F​=(∑i,j​Aij2​)1/2. Given absolute accuracy ε>0\varepsilon>0ε>0 and failure probability 0<δ<10<\delta<10<δ<1, there are fixed input-taking classical and quantum circuit families, with classical preprocessing time O~(Kn2)\widetilde O(Kn^2)O(Kn2), which return classical matrices CclC_{\rm cl}Ccl​ and CqC_{\rm q}Cq​ satisfying

Pr⁡ ⁣[∥Ccl−A1⋯AK∥F≤ε]≥1−δ,Pr⁡ ⁣[max⁡i,j∣(Cq−A1⋯AK)ij∣≤ε]≥1−δ.\Pr\!\left[\|C_{\rm cl}-A_1\cdots A_K\|_F\le\varepsilon\right]\ge1-\delta, \qquad \Pr\!\left[\max_{i,j}|(C_{\rm q}-A_1\cdots A_K)_{ij}|\le\varepsilon\right]\ge1-\delta.Pr[∥Ccl​−A1​⋯AK​∥F​≤ε]≥1−δ,Pr[i,jmax​∣(Cq​−A1​⋯AK​)ij​∣≤ε]≥1−δ.

Apart from input/output and preprocessing overhead, their running times are respectively

O~ ⁣(n2(3KF2ε2)ω−2),O~ ⁣(n23KFε).\widetilde O\!\left(n^2\left(\frac{3^K F^2}{\varepsilon^2}\right)^{\omega-2}\right), \qquad \widetilde O\!\left(n^2\frac{3^K F}{\varepsilon}\right).O(n2(ε23KF2​)ω−2),O(n2ε3KF​).

The soft factors include the confidence logarithms and are uniform over dimensions, factors, matrix entries, accuracy, and confidence; constants may depend on the chosen multiplication implementation. Real numbers are represented exactly, and fixed-position retrieval and arithmetic are charged in both models. The quantum output is an ordinary classical matrix. No efficiently addressable classical or quantum memory is required.

The case K=1K=1K=1 returns the input matrix exactly. For K>1K>1K>1 and F≤εF\le\varepsilonF≤ε, both families return zero; this includes every zero factor. These branches still pay for the input and classical output. The displayed online scales are clamped below by n2n^2n2, and the formal total bound includes Kn2Kn^2Kn2 explicitly. This result compares approximate products in two different error norms under the same circuit access model.

Formalization Note Lean uses k=K−1k=K-1k=K−1 interfaces and computes F2F^2F2 during charged classical preprocessing. Rounded, confidence-dependent sample budgets select members of circuit families fixed before the matrices. The classical law is computed from one fixed list of exact-real arithmetic, random-coin and comparison instructions, with each comparison writing a 0/1 register value and every instruction charged; quantum probabilities and work are computed from the frozen exact-real mean-estimation circuit language. No approximation guarantee or arbitrary runtime number is assumed as a field of an algorithm.

Target

Theorem 1.3 (continues on p.6); Theorems 4.10–4.11, pp.21–23

Fix a classical exact-arithmetic matrix multiplication implementation with achievable exponent ω≥2\omega\ge 2ω≥2. Let n≥1n\ge1n≥1, K≥1K\ge1K≥1, and let A1,…,AK∈Rn×nA_1,\ldots,A_K\in\mathbb R^{n\times n}A1​,…,AK​∈Rn×n be arbitrary matrices. Write F=∏j=1K∥Aj∥FF=\prod_{j=1}^K\|A_j\|_FF=∏j=1K​∥Aj​∥F​, where ∥A∥F=(∑i,jAij2)1/2\|A\|_F=(\sum_{i,j}A_{ij}^2)^{1/2}∥A∥F​=(∑i,j​Aij2​)1/2. Given absolute accuracy ε>0\varepsilon>0ε>0 and failure probability 0<δ<10<\delta<10<δ<1, there are fixed input-taking classical and quantum circuit families, with classical preprocessing time O~(Kn2)\widetilde O(Kn^2)O(Kn2), which return classical matrices CclC_{\rm cl}Ccl​ and CqC_{\rm q}Cq​ satisfying

Pr⁡ ⁣[∥Ccl−A1⋯AK∥F≤ε]≥1−δ,Pr⁡ ⁣[max⁡i,j∣(Cq−A1⋯AK)ij∣≤ε]≥1−δ.\Pr\!\left[\|C_{\rm cl}-A_1\cdots A_K\|_F\le\varepsilon\right]\ge1-\delta, \qquad \Pr\!\left[\max_{i,j}|(C_{\rm q}-A_1\cdots A_K)_{ij}|\le\varepsilon\right]\ge1-\delta.Pr[∥Ccl​−A1​⋯AK​∥F​≤ε]≥1−δ,Pr[i,jmax​∣(Cq​−A1​⋯AK​)ij​∣≤ε]≥1−δ.

Apart from input/output and preprocessing overhead, their running times are respectively

O~ ⁣(n2(3KF2ε2)ω−2),O~ ⁣(n23KFε).\widetilde O\!\left(n^2\left(\frac{3^K F^2}{\varepsilon^2}\right)^{\omega-2}\right), \qquad \widetilde O\!\left(n^2\frac{3^K F}{\varepsilon}\right).O(n2(ε23KF2​)ω−2),O(n2ε3KF​).

The soft factors include the confidence logarithms and are uniform over dimensions, factors, matrix entries, accuracy, and confidence; constants may depend on the chosen multiplication implementation. Real numbers are represented exactly, and fixed-position retrieval and arithmetic are charged in both models. The quantum output is an ordinary classical matrix. No efficiently addressable classical or quantum memory is required.

The case K=1K=1K=1 returns the input matrix exactly. For K>1K>1K>1 and F≤εF\le\varepsilonF≤ε, both families return zero; this includes every zero factor. These branches still pay for the input and classical output. The displayed online scales are clamped below by n2n^2n2, and the formal total bound includes Kn2Kn^2Kn2 explicitly. This result compares approximate products in two different error norms under the same circuit access model.

Formalization Note Lean uses k=K−1k=K-1k=K−1 interfaces and computes F2F^2F2 during charged classical preprocessing. Rounded, confidence-dependent sample budgets select members of circuit families fixed before the matrices. The classical law is computed from one fixed list of exact-real arithmetic, random-coin and comparison instructions, with each comparison writing a 0/1 register value and every instruction charged; quantum probabilities and work are computed from the frozen exact-real mean-estimation circuit language. No approximation guarantee or arbitrary runtime number is assumed as a field of an algorithm.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Randomized and quantum approximate matrix multiplication, arXiv:2510.08509v1. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
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OptimizationQuantum Information·Captain: Goku

Fast Convex Optimization with Quantum Gradient MethodsResearch Paper

Motivation

Fast Convex Optimization with Quantum Gradient Methods establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let X⊆RdX\subseteq\mathbb R^dX⊆Rd be closed, bounded and convex, let x1∈Xx_1\in Xx1​∈X, and let f:Rd→Rf:\mathbb R^d\to\mathbb Rf:Rd→R be convex and ambient GGG-Lipschitz in the stated norm. Assume an attained constrained optimum x⋆x^\starx⋆, and 0<ε<10<\varepsilon<10<ε<1. Both branches use coherent binary evaluations on sufficiently fine finite translated hypergrids: every grid index is preserved, the encoded value has error strictly below θ\thetaθ, and calls to the unitary and its adjoint are counted. The algorithm construction is fixed before the objective, optimum and oracle values; only geometry and supplied numerical scale bounds enter its construction.

  1. Euclidean branch. Set R=∥x1−x⋆∥2R=\|x_1-x^\star\|_2R=∥x1​−x⋆∥2​, K=diam⁡2(X)K=\operatorname{diam}_2(X)K=diam2​(X), T=max⁡{1,⌈(3GR/ε)2⌉}T=\max\{1,\lceil(3GR/\varepsilon)^2\rceil\}T=max{1,⌈(3GR/ε)2⌉}, r1=ε/(6Gd)r_1=\varepsilon/(6G\sqrt d)r1​=ε/(6Gd​), ρ=1/(3T)\rho=1/(3T)ρ=1/(3T), and η=R/(GT)\eta=R/(G\sqrt T)η=R/(GT​). QPSM uses the actual Jordan subgradient-output law of Lemma A.1 at each current center, followed by the supplied exact Euclidean projection. For positive d,G,R,θd,G,R,\thetad,G,R,θ, impose θ≤r1dG/ρ\theta\le r_1dG/\rhoθ≤r1​dG/ρ and the independent-diameter precision budget
234θd4RT ρr1+(23d)2KθGρr1≤ε3.23^4\frac{\theta d^4R}{\sqrt T\,\rho r_1} +(23d)^2K\sqrt{\frac{\theta G}{\rho r_1}}\le\frac{\varepsilon}{3}.234T​ρr1​θd4R​+(23d)2Kρr1​θG​​≤3ε​.

A sufficient scale is a small absolute constant times

min⁡{ε3G2R2d9/2,ε5G4R2K2d9/2,r1dGρ}.\min\left\{\frac{\varepsilon^3}{G^2R^2d^{9/2}}, \frac{\varepsilon^5}{G^4R^2K^2d^{9/2}}, \frac{r_1dG}{\rho}\right\}.min{G2R2d9/2ε3​,G4R2K2d9/2ε5​,ρr1​dG​}.
  1. Mirror branch. Fix p∈[1,∞]p\in[1,\infty]p∈[1,∞], p≠2p\ne2p=2, and its Hölder-conjugate exponent. Let PPP be open convex, X⊆P‾X\subseteq\overline PX⊆P, X∩P≠∅X\cap P\ne\varnothingX∩P=∅, and x1,x⋆∈X∩Px_1,x^\star\in X\cap Px1​,x⋆∈X∩P. The supplied mirror map Φ\PhiΦ is strictly convex and differentiable on PPP, its gradient takes every dual value and diverges at the boundary, and it is μ\muμ-strongly convex on X∩PX\cap PX∩P in the chosen norm, with μ>0\mu>0μ>0. Exact inverse-gradient operations and attained Bregman projections are supplied. Define R=DΦ(x⋆,x1)R=\sqrt{D_\Phi(x^\star,x_1)}R=DΦ​(x⋆,x1​)​, K=diam⁡p(X)K=\operatorname{diam}_p(X)K=diamp​(X), T=max⁡{1,⌈(6GR/(με))2⌉}T=\max\{1,\lceil(6GR/(\sqrt\mu\varepsilon))^2\rceil\}T=max{1,⌈(6GR/(μ​ε))2⌉}, r1=ε/(6Gϑ)r_1=\varepsilon/(6G\vartheta)r1​=ε/(6Gϑ), ρ=1/(3T)\rho=1/(3T)ρ=1/(3T), and η=(R/G)μ/T\eta=(R/G)\sqrt{\mu/T}η=(R/G)μ/T​. Here 1≤ϑ,ϑ⋆≤d1\le\vartheta,\vartheta_\star\le d1≤ϑ,ϑ⋆​≤d, ϑϑ⋆≤d\vartheta\vartheta_\star\le dϑϑ⋆​≤d, ∥v∥p≤ϑ∥v∥∞\|v\|_p\le\vartheta\|v\|_\infty∥v∥p​≤ϑ∥v∥∞​, and ∥g∥⋆≤ϑ⋆∥g∥∞\|g\|_\star\le\vartheta_\star\|g\|_\infty∥g∥⋆​≤ϑ⋆​∥g∥∞​. Require θ≤r1dG/ρ\theta\le r_1dG/\rhoθ≤r1​dG/ρ and
2GRμT+232ϑ⋆Kθd3Gρr1+2Gϑr1+234ϑ⋆2RμTθd3ρr1≤ε.\frac{2GR}{\sqrt{\mu T}} +23^2\vartheta_\star K\sqrt{\frac{\theta d^3G}{\rho r_1}} +2G\vartheta r_1 +23^4\vartheta_\star^2\frac{R}{\sqrt{\mu T}}\frac{\theta d^3}{\rho r_1} \le\varepsilon.μT​2GR​+232ϑ⋆​Kρr1​θd3G​​+2Gϑr1​+234ϑ⋆2​μT​R​ρr1​θd3​≤ε.

This retains both noise terms; a sufficient positive precision takes the minimum of the lemma guard and small absolute multiples of με5/(G4R2K2ϑ⋆2ϑd3)\mu\varepsilon^5/(G^4R^2K^2\vartheta_\star^2\vartheta d^3)με5/(G4R2K2ϑ⋆2​ϑd3) and με3/(G2R2ϑ⋆2ϑd3)\mu\varepsilon^3/(G^2R^2\vartheta_\star^2\vartheta d^3)με3/(G2R2ϑ⋆2​ϑd3).

In either branch the classical output is the average of the first TTT iterates, and

Pr⁡[xˉ∈X, f(xˉ)−f(x⋆)≤ε]≥2/3.\Pr[\bar x\in X,\ f(\bar x)-f(x^\star)\le\varepsilon]\ge2/3.Pr[xˉ∈X, f(xˉ)−f(x⋆)≤ε]≥2/3.

The query costs are O(Tmax⁡{1,log⁡(3dT)})O(T\max\{1,\log(3dT)\})O(Tmax{1,log(3dT)}), with absolute constants common to all data, yielding O~((GR/ε)2)\widetilde O((GR/\varepsilon)^2)O((GR/ε)2) and O~((GR/(με))2)\widetilde O((GR/(\sqrt\mu\varepsilon))^2)O((GR/(μ​ε))2), respectively. Quantum arithmetic uses O~(dT)\widetilde O(dT)O(dT) gates, with binary word length and inverse precision exposed as polynomial arithmetic factors. Supplied geometric operations cost at most T(TΠ+1)T(T_\Pi+1)T(TΠ​+1) and TTnextTT_{\rm next}TTnext​, respectively. All bounds apply on positive-probability branches. Conditional per-call failure control suffices; independence is not assumed.

Zero-dimensional, constant-objective, zero-radius, singleton, or already-accurate regimes return the feasible start with zero queries before divisions. In particular, a start is already accurate if ε≥GK\varepsilon\ge GKε≥GK, or ε≥GR\varepsilon\ge GRε≥GR in the Euclidean branch, or ε≥GR2/μ\varepsilon\ge GR\sqrt{2/\mu}ε≥GR2/μ​ in the mirror branch.

The result shows that quantum zeroth-order methods attain the corresponding first-order nonsmooth query rates. Formalization Note: This uses the formal appendix scope, including ambient Lipschitz control, rather than the informal “on XXX” access description. The Euclidean precision corrects B.3's omitted independent KKK; its printed R4R^4R4 denominator follows in the domain-radius regime K≤2RK\le2RK≤2R, which is not implied by an initial distance. The mirror radius is computed from the Bregman divergence, not introduced by an arbitrary equality. The finite-grid compilation and adaptive execution definitions are submitted for local definition review.

Target

Theorem 2.1; formal Theorems B.3 and C.1

Let X⊆RdX\subseteq\mathbb R^dX⊆Rd be closed, bounded and convex, let x1∈Xx_1\in Xx1​∈X, and let f:Rd→Rf:\mathbb R^d\to\mathbb Rf:Rd→R be convex and ambient GGG-Lipschitz in the stated norm. Assume an attained constrained optimum x⋆x^\starx⋆, and 0<ε<10<\varepsilon<10<ε<1. Both branches use coherent binary evaluations on sufficiently fine finite translated hypergrids: every grid index is preserved, the encoded value has error strictly below θ\thetaθ, and calls to the unitary and its adjoint are counted. The algorithm construction is fixed before the objective, optimum and oracle values; only geometry and supplied numerical scale bounds enter its construction.

  1. Euclidean branch. Set R=∥x1−x⋆∥2R=\|x_1-x^\star\|_2R=∥x1​−x⋆∥2​, K=diam⁡2(X)K=\operatorname{diam}_2(X)K=diam2​(X), T=max⁡{1,⌈(3GR/ε)2⌉}T=\max\{1,\lceil(3GR/\varepsilon)^2\rceil\}T=max{1,⌈(3GR/ε)2⌉}, r1=ε/(6Gd)r_1=\varepsilon/(6G\sqrt d)r1​=ε/(6Gd​), ρ=1/(3T)\rho=1/(3T)ρ=1/(3T), and η=R/(GT)\eta=R/(G\sqrt T)η=R/(GT​). QPSM uses the actual Jordan subgradient-output law of Lemma A.1 at each current center, followed by the supplied exact Euclidean projection. For positive d,G,R,θd,G,R,\thetad,G,R,θ, impose θ≤r1dG/ρ\theta\le r_1dG/\rhoθ≤r1​dG/ρ and the independent-diameter precision budget
234θd4RT ρr1+(23d)2KθGρr1≤ε3.23^4\frac{\theta d^4R}{\sqrt T\,\rho r_1} +(23d)^2K\sqrt{\frac{\theta G}{\rho r_1}}\le\frac{\varepsilon}{3}.234T​ρr1​θd4R​+(23d)2Kρr1​θG​​≤3ε​.

A sufficient scale is a small absolute constant times

min⁡{ε3G2R2d9/2,ε5G4R2K2d9/2,r1dGρ}.\min\left\{\frac{\varepsilon^3}{G^2R^2d^{9/2}}, \frac{\varepsilon^5}{G^4R^2K^2d^{9/2}}, \frac{r_1dG}{\rho}\right\}.min{G2R2d9/2ε3​,G4R2K2d9/2ε5​,ρr1​dG​}.
  1. Mirror branch. Fix p∈[1,∞]p\in[1,\infty]p∈[1,∞], p≠2p\ne2p=2, and its Hölder-conjugate exponent. Let PPP be open convex, X⊆P‾X\subseteq\overline PX⊆P, X∩P≠∅X\cap P\ne\varnothingX∩P=∅, and x1,x⋆∈X∩Px_1,x^\star\in X\cap Px1​,x⋆∈X∩P. The supplied mirror map Φ\PhiΦ is strictly convex and differentiable on PPP, its gradient takes every dual value and diverges at the boundary, and it is μ\muμ-strongly convex on X∩PX\cap PX∩P in the chosen norm, with μ>0\mu>0μ>0. Exact inverse-gradient operations and attained Bregman projections are supplied. Define R=DΦ(x⋆,x1)R=\sqrt{D_\Phi(x^\star,x_1)}R=DΦ​(x⋆,x1​)​, K=diam⁡p(X)K=\operatorname{diam}_p(X)K=diamp​(X), T=max⁡{1,⌈(6GR/(με))2⌉}T=\max\{1,\lceil(6GR/(\sqrt\mu\varepsilon))^2\rceil\}T=max{1,⌈(6GR/(μ​ε))2⌉}, r1=ε/(6Gϑ)r_1=\varepsilon/(6G\vartheta)r1​=ε/(6Gϑ), ρ=1/(3T)\rho=1/(3T)ρ=1/(3T), and η=(R/G)μ/T\eta=(R/G)\sqrt{\mu/T}η=(R/G)μ/T​. Here 1≤ϑ,ϑ⋆≤d1\le\vartheta,\vartheta_\star\le d1≤ϑ,ϑ⋆​≤d, ϑϑ⋆≤d\vartheta\vartheta_\star\le dϑϑ⋆​≤d, ∥v∥p≤ϑ∥v∥∞\|v\|_p\le\vartheta\|v\|_\infty∥v∥p​≤ϑ∥v∥∞​, and ∥g∥⋆≤ϑ⋆∥g∥∞\|g\|_\star\le\vartheta_\star\|g\|_\infty∥g∥⋆​≤ϑ⋆​∥g∥∞​. Require θ≤r1dG/ρ\theta\le r_1dG/\rhoθ≤r1​dG/ρ and
2GRμT+232ϑ⋆Kθd3Gρr1+2Gϑr1+234ϑ⋆2RμTθd3ρr1≤ε.\frac{2GR}{\sqrt{\mu T}} +23^2\vartheta_\star K\sqrt{\frac{\theta d^3G}{\rho r_1}} +2G\vartheta r_1 +23^4\vartheta_\star^2\frac{R}{\sqrt{\mu T}}\frac{\theta d^3}{\rho r_1} \le\varepsilon.μT​2GR​+232ϑ⋆​Kρr1​θd3G​​+2Gϑr1​+234ϑ⋆2​μT​R​ρr1​θd3​≤ε.

This retains both noise terms; a sufficient positive precision takes the minimum of the lemma guard and small absolute multiples of με5/(G4R2K2ϑ⋆2ϑd3)\mu\varepsilon^5/(G^4R^2K^2\vartheta_\star^2\vartheta d^3)με5/(G4R2K2ϑ⋆2​ϑd3) and με3/(G2R2ϑ⋆2ϑd3)\mu\varepsilon^3/(G^2R^2\vartheta_\star^2\vartheta d^3)με3/(G2R2ϑ⋆2​ϑd3).

In either branch the classical output is the average of the first TTT iterates, and

Pr⁡[xˉ∈X, f(xˉ)−f(x⋆)≤ε]≥2/3.\Pr[\bar x\in X,\ f(\bar x)-f(x^\star)\le\varepsilon]\ge2/3.Pr[xˉ∈X, f(xˉ)−f(x⋆)≤ε]≥2/3.

The query costs are O(Tmax⁡{1,log⁡(3dT)})O(T\max\{1,\log(3dT)\})O(Tmax{1,log(3dT)}), with absolute constants common to all data, yielding O~((GR/ε)2)\widetilde O((GR/\varepsilon)^2)O((GR/ε)2) and O~((GR/(με))2)\widetilde O((GR/(\sqrt\mu\varepsilon))^2)O((GR/(μ​ε))2), respectively. Quantum arithmetic uses O~(dT)\widetilde O(dT)O(dT) gates, with binary word length and inverse precision exposed as polynomial arithmetic factors. Supplied geometric operations cost at most T(TΠ+1)T(T_\Pi+1)T(TΠ​+1) and TTnextTT_{\rm next}TTnext​, respectively. All bounds apply on positive-probability branches. Conditional per-call failure control suffices; independence is not assumed.

Zero-dimensional, constant-objective, zero-radius, singleton, or already-accurate regimes return the feasible start with zero queries before divisions. In particular, a start is already accurate if ε≥GK\varepsilon\ge GKε≥GK, or ε≥GR\varepsilon\ge GRε≥GR in the Euclidean branch, or ε≥GR2/μ\varepsilon\ge GR\sqrt{2/\mu}ε≥GR2/μ​ in the mirror branch.

The result shows that quantum zeroth-order methods attain the corresponding first-order nonsmooth query rates. Formalization Note: This uses the formal appendix scope, including ambient Lipschitz control, rather than the informal “on XXX” access description. The Euclidean precision corrects B.3's omitted independent KKK; its printed R4R^4R4 denominator follows in the domain-radius regime K≤2RK\le2RK≤2R, which is not implied by an initial distance. The mirror radius is computed from the Bregman divergence, not introduced by an arbitrary equality. The finite-grid compilation and adaptive execution definitions are submitted for local definition review.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Fast Convex Optimization with Quantum Gradient Methods, arXiv:2503.17356v2. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Information·Captain: Goku

Quantum Signal Processing and Quantum Singular Value Transformation on U(N)U(N)U(N)Research Paper

Motivation

Quantum Signal Processing and Quantum Singular Value Transformation on U(N)U(N)U(N) establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let d≥0d\geq 0d≥0 be an integer and let P=(Pkj)P=(P_{kj})P=(Pkj​) be an r×cr\times cr×c matrix of complex polynomials, with r,c≥1r,c\geq 1r,c≥1. Each entry has degree at most ddd and parity ddd: Pkj(−x)=(−1)dPkj(x)P_{kj}(-x)=(-1)^dP_{kj}(x)Pkj​(−x)=(−1)dPkj​(x). Suppose

Ic−P(x)†P(x)⪰0for every x∈[−1,1].I_c-P(x)^\dagger P(x)\succeq 0\qquad\text{for every }x\in[-1,1].Ic​−P(x)†P(x)⪰0for every x∈[−1,1].

Let I,O,K\mathcal I,\mathcal O,\mathcal KI,O,K be positive finite input, output, and signal registers, and fix known isometric computational-basis embeddings ι:I↪K\iota:\mathcal I\hookrightarrow\mathcal Kι:I↪K and ω:O↪K\omega:\mathcal O\hookrightarrow\mathcal Kω:O↪K. The mixing register has qqq qubits, with fixed embeddings of the ccc input labels and rrr output labels in its 2q2^q2q basis states; unused rows and columns are zero padded. An admissible oracle is any unitary UUU on K\mathcal KK with exact unscaled block A=U[ω,ι]:I→OA=U[\omega,\iota]:\mathcal I\to\mathcal OA=U[ω,ι]:I→O.

There are d+1d+1d+1 known unitary mixers on the mixing register enlarged by one flag qubit, and a fixed identification of the flag and mixing registers, chosen from P,dP,dP,d and the known embeddings before UUU or AAA is supplied. The resulting synthesis circuit alternates these known operations with exactly ddd uncontrolled oracle calls U,U†,U,U†,…U,U^\dagger,U,U^\dagger,\ldotsU,U†,U,U†,…. A mixer acts conditioned on the known input signal projector at even stages and the known output signal projector at odd stages. For every admissible oracle and every family of input vectors ϕj∈I\phi_j\in\mathcal Iϕj​∈I, the entire flag-zero component of its output is

∣0⟩flag∑k=1r∣k⟩mix ιd ⁣(∑j=1cPkj(SV)(A)ϕj).|0\rangle_{\mathrm{flag}}\sum_{k=1}^{r}|k\rangle_{\mathrm{mix}}\,\iota_d\!\left(\sum_{j=1}^{c}P_{kj}^{(\mathrm{SV})}(A)\phi_j\right).∣0⟩flag​k=1∑r​∣k⟩mix​ιd​(j=1∑c​Pkj(SV)​(A)ϕj​).

Here the input is ∣0⟩flag∑j=1c∣j⟩mix ι(ϕj)|0\rangle_{\mathrm{flag}}\sum_{j=1}^{c}|j\rangle_{\mathrm{mix}}\,\iota(\phi_j)∣0⟩flag​∑j=1c​∣j⟩mix​ι(ϕj​), and ιd=ι\iota_d=\iotaιd​=ι for even ddd and ιd=ω\iota_d=\omegaιd​=ω for odd ddd. Writing Pkj(x)=∑apkj,axaP_{kj}(x)=\sum_a p_{kj,a}x^aPkj​(x)=∑a​pkj,a​xa, the singular-value transforms are

Pkj(SV)(A)={∑a=0⌊d/2⌋pkj,2a(A†A)a,d even,∑a=0⌊d/2⌋pkj,2a+1A(A†A)a,d odd.P_{kj}^{(\mathrm{SV})}(A)= \begin{cases} \displaystyle\sum_{a=0}^{\lfloor d/2\rfloor}p_{kj,2a}(A^\dagger A)^a,&d\text{ even},\\[4pt] \displaystyle\sum_{a=0}^{\lfloor d/2\rfloor}p_{kj,2a+1}A(A^\dagger A)^a,&d\text{ odd}. \end{cases}Pkj(SV)​(A)=⎩⎨⎧​a=0∑⌊d/2⌋​pkj,2a​(A†A)a,a=0∑⌊d/2⌋​pkj,2a+1​A(A†A)a,​d even,d odd.​

All remaining amplitude lies in flag one. This simultaneously block-encodes the whole polynomial matrix at normalization one and error zero, without a positive success-probability guarantee. The formula includes the input kernel in the even case, where the constant coefficient acts as a multiple of the identity. Singular AAA, rectangular AAA and PPP, zero PPP, and d=0d=0d=0 are permitted. A normalized joint input gives a physical state, while the equality itself is linear and holds for all vectors.

This theorem supplies coherent matrix-valued singular-value synthesis under a single matrix contraction condition. No Hermiticity, invertibility, determinant constraint, finite gate set, or classical synthesis-time estimate is imposed.

Formalization Note The printed Theorem 10 omits the degree and common-parity requirements used by its proof; these are explicit here. The output signal zero register and the orientation of the singular-vector decomposition are corrected according to Eqs. (1) and (31)–(35). The printed claim and these corrections are recorded separately in the audit notes. Known embeddings express the all-zero signal-ancilla subspaces in register-independent coordinates.

Target

Theorem 10 (U(N)-QSVT, backward), §2.3, Eq. (38), pp. 7–8

Let d≥0d\geq 0d≥0 be an integer and let P=(Pkj)P=(P_{kj})P=(Pkj​) be an r×cr\times cr×c matrix of complex polynomials, with r,c≥1r,c\geq 1r,c≥1. Each entry has degree at most ddd and parity ddd: Pkj(−x)=(−1)dPkj(x)P_{kj}(-x)=(-1)^dP_{kj}(x)Pkj​(−x)=(−1)dPkj​(x). Suppose

Ic−P(x)†P(x)⪰0for every x∈[−1,1].I_c-P(x)^\dagger P(x)\succeq 0\qquad\text{for every }x\in[-1,1].Ic​−P(x)†P(x)⪰0for every x∈[−1,1].

Let I,O,K\mathcal I,\mathcal O,\mathcal KI,O,K be positive finite input, output, and signal registers, and fix known isometric computational-basis embeddings ι:I↪K\iota:\mathcal I\hookrightarrow\mathcal Kι:I↪K and ω:O↪K\omega:\mathcal O\hookrightarrow\mathcal Kω:O↪K. The mixing register has qqq qubits, with fixed embeddings of the ccc input labels and rrr output labels in its 2q2^q2q basis states; unused rows and columns are zero padded. An admissible oracle is any unitary UUU on K\mathcal KK with exact unscaled block A=U[ω,ι]:I→OA=U[\omega,\iota]:\mathcal I\to\mathcal OA=U[ω,ι]:I→O.

There are d+1d+1d+1 known unitary mixers on the mixing register enlarged by one flag qubit, and a fixed identification of the flag and mixing registers, chosen from P,dP,dP,d and the known embeddings before UUU or AAA is supplied. The resulting synthesis circuit alternates these known operations with exactly ddd uncontrolled oracle calls U,U†,U,U†,…U,U^\dagger,U,U^\dagger,\ldotsU,U†,U,U†,…. A mixer acts conditioned on the known input signal projector at even stages and the known output signal projector at odd stages. For every admissible oracle and every family of input vectors ϕj∈I\phi_j\in\mathcal Iϕj​∈I, the entire flag-zero component of its output is

∣0⟩flag∑k=1r∣k⟩mix ιd ⁣(∑j=1cPkj(SV)(A)ϕj).|0\rangle_{\mathrm{flag}}\sum_{k=1}^{r}|k\rangle_{\mathrm{mix}}\,\iota_d\!\left(\sum_{j=1}^{c}P_{kj}^{(\mathrm{SV})}(A)\phi_j\right).∣0⟩flag​k=1∑r​∣k⟩mix​ιd​(j=1∑c​Pkj(SV)​(A)ϕj​).

Here the input is ∣0⟩flag∑j=1c∣j⟩mix ι(ϕj)|0\rangle_{\mathrm{flag}}\sum_{j=1}^{c}|j\rangle_{\mathrm{mix}}\,\iota(\phi_j)∣0⟩flag​∑j=1c​∣j⟩mix​ι(ϕj​), and ιd=ι\iota_d=\iotaιd​=ι for even ddd and ιd=ω\iota_d=\omegaιd​=ω for odd ddd. Writing Pkj(x)=∑apkj,axaP_{kj}(x)=\sum_a p_{kj,a}x^aPkj​(x)=∑a​pkj,a​xa, the singular-value transforms are

Pkj(SV)(A)={∑a=0⌊d/2⌋pkj,2a(A†A)a,d even,∑a=0⌊d/2⌋pkj,2a+1A(A†A)a,d odd.P_{kj}^{(\mathrm{SV})}(A)= \begin{cases} \displaystyle\sum_{a=0}^{\lfloor d/2\rfloor}p_{kj,2a}(A^\dagger A)^a,&d\text{ even},\\[4pt] \displaystyle\sum_{a=0}^{\lfloor d/2\rfloor}p_{kj,2a+1}A(A^\dagger A)^a,&d\text{ odd}. \end{cases}Pkj(SV)​(A)=⎩⎨⎧​a=0∑⌊d/2⌋​pkj,2a​(A†A)a,a=0∑⌊d/2⌋​pkj,2a+1​A(A†A)a,​d even,d odd.​

All remaining amplitude lies in flag one. This simultaneously block-encodes the whole polynomial matrix at normalization one and error zero, without a positive success-probability guarantee. The formula includes the input kernel in the even case, where the constant coefficient acts as a multiple of the identity. Singular AAA, rectangular AAA and PPP, zero PPP, and d=0d=0d=0 are permitted. A normalized joint input gives a physical state, while the equality itself is linear and holds for all vectors.

This theorem supplies coherent matrix-valued singular-value synthesis under a single matrix contraction condition. No Hermiticity, invertibility, determinant constraint, finite gate set, or classical synthesis-time estimate is imposed.

Formalization Note The printed Theorem 10 omits the degree and common-parity requirements used by its proof; these are explicit here. The output signal zero register and the orientation of the singular-vector decomposition are corrected according to Eqs. (1) and (31)–(35). The printed claim and these corrections are recorded separately in the audit notes. Known embeddings express the all-zero signal-ancilla subspaces in register-independent coordinates.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Quantum Signal Processing and Quantum Singular Value Transformation on U(N)U(N)U(N), arXiv:2408.01439v4. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
OptimizationQuantum Information·Captain: Goku

Quantum speedups for stochastic optimizationResearch Paper

Motivation

Quantum speedups for stochastic optimization establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let d≥1d\ge 1d≥1 and let f:Rd→Rf:\mathbb R^d\to\mathbb Rf:Rd→R be differentiable and globally convex. Suppose fff attains its global minimum at a point x⋆x_\starx⋆​ with ∥x⋆∥2≤R\|x_\star\|_2\le R∥x⋆​∥2​≤R, where L,R≥0L,R\ge0L,R≥0 are public bounds. For every query point xxx, the stochastic gradient is drawn from a measurable probability law satisfying

E[g(x)]=∇f(x),E∥g(x)∥22≤L2.\mathbb E[g(x)]=\nabla f(x),\qquad \mathbb E\|g(x)\|_2^2\le L^2.E[g(x)]=∇f(x),E∥g(x)∥22​≤L2.

Assume coherent unitary access to this gradient law, preserving the query point and allowing arbitrary garbage, and access to the inverse oracle. The implementation uses normalized zero registers, Born measurement laws, and known Gaussian preparation and reordering operations that construct the smoothed oracle with one gradient-oracle call. These operations and the mean-estimation routine are fixed before the unknown objective and oracle. The mean-estimation interface cited on p.8 is realized, rather than assumed as a convergence hypothesis: for any sampling oracle with variance at most L2L^2L2, requested error 0<η≤L0<\eta\le L0<η≤L, and 0<δ<10<\delta<10<δ<1, its execution has total probability one and finite expected calls, and its estimate is within Euclidean distance η\etaη of the mean with probability at least 1−δ1-\delta1−δ.

For any ϵ>0\epsilon>0ϵ>0, run Algorithm 3 with fresh Algorithm 2 gradient estimates. In the nontrivial case L,R>0L,R>0L,R>0 and ϵ<LR\epsilon<LRϵ<LR, its parameters are

T=⌈4d1/4LR/ϵ⌉,σ^=d1/88LϵR,r=ϵ4dL,γ=R6L/r(T+2)3/2σ^.T=\left\lceil4d^{1/4}LR/\epsilon\right\rceil,\quad \widehat\sigma=\frac{d^{1/8}}8\sqrt{\frac{L\epsilon}{R}},\quad r=\frac{\epsilon}{4\sqrt d L},\quad \gamma=\frac{R\sqrt{6L/r}}{(T+2)^{3/2}\widehat\sigma}.T=⌈4d1/4LR/ϵ⌉,σ=8d1/8​RLϵ​​,r=4d​Lϵ​,γ=(T+2)3/2σR6L/r​​.

It starts from x1=x1ag=0x_1=x_1^{\mathrm{ag}}=0x1​=x1ag​=0. At iteration ttt, set βt=(t+1)/2\beta_t=(t+1)/2βt​=(t+1)/2, γt=(t+1)γ/2\gamma_t=(t+1)\gamma/2γt​=(t+1)γ/2, and xtmd=βt−1xt+(1−βt−1)xtagx_t^{\mathrm{md}}=\beta_t^{-1}x_t+(1-\beta_t^{-1})x_t^{\mathrm{ag}}xtmd​=βt−1​xt​+(1−βt−1​)xtag​. Use Algorithm 2 on the Gaussian-smoothed gradient law at xtmdx_t^{\mathrm{md}}xtmd​, then use the printed ball-constrained update

xt+1=arg min⁡∥z∥2≤R{γt⟨g~t,z−xtmd⟩+L2r∥xtmd−z∥22},xt+1ag=βt−1xt+1+(1−βt−1)xtag.x_{t+1}=\operatorname*{arg\,min}_{\|z\|_2\le R} \left\{\gamma_t\langle\widetilde g_t,z-x_t^{\mathrm{md}}\rangle+ \frac L{2r}\|x_t^{\mathrm{md}}-z\|_2^2\right\},\qquad x_{t+1}^{\mathrm{ag}}=\beta_t^{-1}x_{t+1}+(1-\beta_t^{-1})x_t^{\mathrm{ag}}.xt+1​=∥z∥2​≤Rargmin​{γt​⟨g​t​,z−xtmd​⟩+2rL​∥xtmd​−z∥22​},xt+1ag​=βt−1​xt+1​+(1−βt−1​)xtag​.

The returned point is xout=xT+1agx_{\mathrm{out}}=x_{T+1}^{\mathrm{ag}}xout​=xT+1ag​. The same execution, including its classical randomness and quantum measurements, has total probability one and satisfies

E[f(xout)−f(x⋆)]≤ϵ,E[Q]=O~ ⁣(d5/8(LR/ϵ)3/2).\mathbb E[f(x_{\mathrm{out}})-f(x_\star)]\le\epsilon,\qquad \mathbb E[Q]=\widetilde O\!\left(d^{5/8}(LR/\epsilon)^{3/2}\right).E[f(xout​)−f(x⋆​)]≤ϵ,E[Q]=O(d5/8(LR/ϵ)3/2).

Here QQQ counts every call to the original gradient oracle and its inverse. Its expectation is finite; the positive geometric level in Algorithm 2 allows an unbounded query count. Explicitly, there are absolute constants C>0C>0C>0, an integer p≥0p\ge0p≥0, and a threshold a≥1a\ge1a≥1, all independent of the dimension, bounds, accuracy, objective, probability laws, and register realization, such that whenever LR/ϵ≥aLR/\epsilon\ge aLR/ϵ≥a,

E[Q]≤Cd5/8(LR/ϵ)3/2max⁡{1,log⁡(2+d)+∣log⁡ϵ∣+∣log⁡L∣+∣log⁡R∣}p.\mathbb E[Q]\le C d^{5/8}(LR/\epsilon)^{3/2} \max\{1,\log(2+d)+|\log\epsilon|+|\log L|+|\log R|\}^{p}.E[Q]≤Cd5/8(LR/ϵ)3/2max{1,log(2+d)+∣logϵ∣+∣logL∣+∣logR∣}p.

If L=0L=0L=0, R=0R=0R=0, or ϵ≥LR\epsilon\ge LRϵ≥LR, the implementation returns 000 with no queries and retains the expected-accuracy guarantee. The minimizing point x⋆x_\starx⋆​ is used only to express the guarantee and is not supplied to the algorithm. This result gives the expected-query speedup of the paper's quantum accelerated stochastic approximation method; it asserts no gate-complexity or fixed-confidence output bound.

Formalization Note The real iteration budget on p.13 is rounded upward to define a finite loop. The statement preserves the proximal center and all other displayed constants. The p.13/p.15 pointwise gradient assertion is incompatible with the stated second-moment hypothesis; the proof also contains an extra factor 1/r1/r1/r, a reversed optimum-gap sign, and a constant gap in its use of Lemma 5. These are disclosed proof gaps, not additional hypotheses or silent changes to Algorithm 3. No directional-mean definition is imported or reconstructed.

Target

Theorem 5 (Formal version of Theorem 1, Part 1)

Let d≥1d\ge 1d≥1 and let f:Rd→Rf:\mathbb R^d\to\mathbb Rf:Rd→R be differentiable and globally convex. Suppose fff attains its global minimum at a point x⋆x_\starx⋆​ with ∥x⋆∥2≤R\|x_\star\|_2\le R∥x⋆​∥2​≤R, where L,R≥0L,R\ge0L,R≥0 are public bounds. For every query point xxx, the stochastic gradient is drawn from a measurable probability law satisfying

E[g(x)]=∇f(x),E∥g(x)∥22≤L2.\mathbb E[g(x)]=\nabla f(x),\qquad \mathbb E\|g(x)\|_2^2\le L^2.E[g(x)]=∇f(x),E∥g(x)∥22​≤L2.

Assume coherent unitary access to this gradient law, preserving the query point and allowing arbitrary garbage, and access to the inverse oracle. The implementation uses normalized zero registers, Born measurement laws, and known Gaussian preparation and reordering operations that construct the smoothed oracle with one gradient-oracle call. These operations and the mean-estimation routine are fixed before the unknown objective and oracle. The mean-estimation interface cited on p.8 is realized, rather than assumed as a convergence hypothesis: for any sampling oracle with variance at most L2L^2L2, requested error 0<η≤L0<\eta\le L0<η≤L, and 0<δ<10<\delta<10<δ<1, its execution has total probability one and finite expected calls, and its estimate is within Euclidean distance η\etaη of the mean with probability at least 1−δ1-\delta1−δ.

For any ϵ>0\epsilon>0ϵ>0, run Algorithm 3 with fresh Algorithm 2 gradient estimates. In the nontrivial case L,R>0L,R>0L,R>0 and ϵ<LR\epsilon<LRϵ<LR, its parameters are

T=⌈4d1/4LR/ϵ⌉,σ^=d1/88LϵR,r=ϵ4dL,γ=R6L/r(T+2)3/2σ^.T=\left\lceil4d^{1/4}LR/\epsilon\right\rceil,\quad \widehat\sigma=\frac{d^{1/8}}8\sqrt{\frac{L\epsilon}{R}},\quad r=\frac{\epsilon}{4\sqrt d L},\quad \gamma=\frac{R\sqrt{6L/r}}{(T+2)^{3/2}\widehat\sigma}.T=⌈4d1/4LR/ϵ⌉,σ=8d1/8​RLϵ​​,r=4d​Lϵ​,γ=(T+2)3/2σR6L/r​​.

It starts from x1=x1ag=0x_1=x_1^{\mathrm{ag}}=0x1​=x1ag​=0. At iteration ttt, set βt=(t+1)/2\beta_t=(t+1)/2βt​=(t+1)/2, γt=(t+1)γ/2\gamma_t=(t+1)\gamma/2γt​=(t+1)γ/2, and xtmd=βt−1xt+(1−βt−1)xtagx_t^{\mathrm{md}}=\beta_t^{-1}x_t+(1-\beta_t^{-1})x_t^{\mathrm{ag}}xtmd​=βt−1​xt​+(1−βt−1​)xtag​. Use Algorithm 2 on the Gaussian-smoothed gradient law at xtmdx_t^{\mathrm{md}}xtmd​, then use the printed ball-constrained update

xt+1=arg min⁡∥z∥2≤R{γt⟨g~t,z−xtmd⟩+L2r∥xtmd−z∥22},xt+1ag=βt−1xt+1+(1−βt−1)xtag.x_{t+1}=\operatorname*{arg\,min}_{\|z\|_2\le R} \left\{\gamma_t\langle\widetilde g_t,z-x_t^{\mathrm{md}}\rangle+ \frac L{2r}\|x_t^{\mathrm{md}}-z\|_2^2\right\},\qquad x_{t+1}^{\mathrm{ag}}=\beta_t^{-1}x_{t+1}+(1-\beta_t^{-1})x_t^{\mathrm{ag}}.xt+1​=∥z∥2​≤Rargmin​{γt​⟨g​t​,z−xtmd​⟩+2rL​∥xtmd​−z∥22​},xt+1ag​=βt−1​xt+1​+(1−βt−1​)xtag​.

The returned point is xout=xT+1agx_{\mathrm{out}}=x_{T+1}^{\mathrm{ag}}xout​=xT+1ag​. The same execution, including its classical randomness and quantum measurements, has total probability one and satisfies

E[f(xout)−f(x⋆)]≤ϵ,E[Q]=O~ ⁣(d5/8(LR/ϵ)3/2).\mathbb E[f(x_{\mathrm{out}})-f(x_\star)]\le\epsilon,\qquad \mathbb E[Q]=\widetilde O\!\left(d^{5/8}(LR/\epsilon)^{3/2}\right).E[f(xout​)−f(x⋆​)]≤ϵ,E[Q]=O(d5/8(LR/ϵ)3/2).

Here QQQ counts every call to the original gradient oracle and its inverse. Its expectation is finite; the positive geometric level in Algorithm 2 allows an unbounded query count. Explicitly, there are absolute constants C>0C>0C>0, an integer p≥0p\ge0p≥0, and a threshold a≥1a\ge1a≥1, all independent of the dimension, bounds, accuracy, objective, probability laws, and register realization, such that whenever LR/ϵ≥aLR/\epsilon\ge aLR/ϵ≥a,

E[Q]≤Cd5/8(LR/ϵ)3/2max⁡{1,log⁡(2+d)+∣log⁡ϵ∣+∣log⁡L∣+∣log⁡R∣}p.\mathbb E[Q]\le C d^{5/8}(LR/\epsilon)^{3/2} \max\{1,\log(2+d)+|\log\epsilon|+|\log L|+|\log R|\}^{p}.E[Q]≤Cd5/8(LR/ϵ)3/2max{1,log(2+d)+∣logϵ∣+∣logL∣+∣logR∣}p.

If L=0L=0L=0, R=0R=0R=0, or ϵ≥LR\epsilon\ge LRϵ≥LR, the implementation returns 000 with no queries and retains the expected-accuracy guarantee. The minimizing point x⋆x_\starx⋆​ is used only to express the guarantee and is not supplied to the algorithm. This result gives the expected-query speedup of the paper's quantum accelerated stochastic approximation method; it asserts no gate-complexity or fixed-confidence output bound.

Formalization Note The real iteration budget on p.13 is rounded upward to define a finite loop. The statement preserves the proximal center and all other displayed constants. The p.13/p.15 pointwise gradient assertion is incompatible with the stated second-moment hypothesis; the proof also contains an extra factor 1/r1/r1/r, a reversed optimum-gap sign, and a constant gap in its use of Lemma 5. These are disclosed proof gaps, not additional hypotheses or silent changes to Algorithm 3. No directional-mean definition is imported or reconstructed.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Quantum speedups for stochastic optimization, arXiv:2308.01582v2. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Information·Captain: Goku

The Quantum Esscher TransformResearch Paper

Motivation

The Quantum Esscher Transform establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let d≥1d\ge1d≥1, n,a,nρ≥0n,a,n_\rho\ge0n,a,nρ​≥0, θ∈Rd\theta\in\mathbb R^dθ∈Rd, and κ>1\kappa>1κ>1 be public parameters. Set

β=∑j=1d∣θj∣+2(1+log⁡2(2κ)),L=log⁡2(1/ε),εBE=(ε8L)2,\beta=\sum_{j=1}^d|\theta_j|+2(1+\log_2(2\kappa)),\qquad L=\log_2(1/\varepsilon),\qquad \varepsilon_{\rm BE}=\left(\frac{\varepsilon}{8L}\right)^2,β=j=1∑d​∣θj​∣+2(1+log2​(2κ)),L=log2​(1/ε),εBE​=(8Lε​)2,

where 0<ε<2−β0<\varepsilon<2^{-\beta}0<ε<2−β. The input ρ\rhoρ is an nnn-qubit trace-one density operator whose eigenvalues lie in [1/κ,1][1/\kappa,1][1/κ,1]. Each HjH_jHj​ is Hermitian with ∥Hj∥op≤1\|H_j\|_{\rm op}\le1∥Hj​∥op​≤1. Purified access is a unitary OρO_\rhoOρ​ on nρ+nn_\rho+nnρ​+n qubits preparing a purification of ρ\rhoρ, with the nρn_\rhonρ​ ancillary qubits first. Let UρU_\rhoUρ​ be the exact (1,n+nρ,0)(1,n+n_\rho,0)(1,n+nρ​,0) block-encoding supplied by the purification construction of Proposition 12. For each jjj, supplied UjU_jUj​ is a (1,a,εBE)(1,a,\varepsilon_{\rm BE})(1,a,εBE​) block-encoding of HjH_jHj​; ordinary, adjoint and controlled signal access are available.

There are universal constants Cρ,Cobs>0C_\rho,C_{\rm obs}>0Cρ​,Cobs​>0, a nonnegative integer ppp, and a universal threshold 0<ε0<10<\varepsilon_0<10<ε0​<1 such that, for every admissible public parameter choice with ε≤ε0\varepsilon\le\varepsilon_0ε≤ε0​, a QEsscher circuit can be selected before ρ,Hj,Oρ,Uj\rho,H_j,O_\rho,U_jρ,Hj​,Oρ​,Uj​. This circuit is the logarithm transformation, coefficient state-preparation pair, padded linear combination, and exponential transformation of Algorithm 1. It works for every admissible hidden input and oracle completion. With b=⌈log⁡2(d+1)⌉b=\lceil\log_2(d+1)\rceilb=⌈log2​(d+1)⌉ and aout=max⁡(a,n+nρ)+b+4a_{\rm out}=\max(a,n+n_\rho)+b+4aout​=max(a,n+nρ​)+b+4, its unitary UoutU_{\rm out}Uout​ satisfies

∥σ−(⟨0aout∣⊗In)Uout(∣0aout⟩⊗In)∥op≤ε,σ=exp⁡ ⁣(∑j=1dθjHj+log⁡2ρ)4eβ.\left\|\sigma-(\langle0^{a_{\rm out}}|\otimes I_n)U_{\rm out}(|0^{a_{\rm out}}\rangle\otimes I_n)\right\|_{\rm op}\le\varepsilon, \qquad \sigma=\frac{\exp\!\left(\sum_{j=1}^d\theta_jH_j+\log_2\rho\right)}{4e^\beta}.∥σ−(⟨0aout​∣⊗In​)Uout​(∣0aout​⟩⊗In​)∥op​≤ε,σ=4eβexp(∑j=1d​θj​Hj​+log2​ρ)​.

Its oracle counts, including ordinary, adjoint and controlled calls, obey

qρ≤CρκL2max⁡ ⁣(1,log⁡2(2+κL2))p,qj≤CobsL(j∈[d]).q_\rho\le C_\rho\kappa L^2\max\!\left(1,\log_2(2+\kappa L^2)\right)^p, \qquad q_j\le C_{\rm obs}L\quad(j\in[d]).qρ​≤Cρ​κL2max(1,log2​(2+κL2))p,qj​≤Cobs​L(j∈[d]).

The logarithm of a positive matrix is defined by applying log⁡2\log_2log2​ to its eigenvalues; exp⁡\expexp is the natural matrix exponential. The constants, exponent and threshold are independent of all public parameters, hidden matrices and oracle implementations.

This supplies the subnormalized transform as a block-encoding, useful as an operator primitive. The query count is for UρU_\rhoUρ​; each such call can be implemented with a constant number of purification-oracle calls. The actual nρn_\rhonρ​ is retained in the footprint; the source's nρ=poly⁡(n)n_\rho=\operatorname{poly}(n)nρ​=poly(n) is a family convention, and no gate-time conclusion is asserted.

Source corrections and limitation. Algorithm 1 and Step 3 print b=⌈log⁡2d⌉b=\lceil\log_2d\rceilb=⌈log2​d⌉, although their d+1d+1d+1 coefficients require b=⌈log⁡2(d+1)⌉b=\lceil\log_2(d+1)\rceilb=⌈log2​(d+1)⌉. The box prints the divisor eβe^\betaeβ; the statement uses proof Step 5's explicit 4eβ4e^\beta4eβ. The printed error schedule is retained. The claim that its numeral 8 ensures Eq. (III.2) has an unresolved quantitative degree-bound gap; accuracy remains the theorem's conclusion, without adding that bound as an assumption.

Target

Theorem 5 (Algorithm 1 and proof, pp.6–7)

Let d≥1d\ge1d≥1, n,a,nρ≥0n,a,n_\rho\ge0n,a,nρ​≥0, θ∈Rd\theta\in\mathbb R^dθ∈Rd, and κ>1\kappa>1κ>1 be public parameters. Set

β=∑j=1d∣θj∣+2(1+log⁡2(2κ)),L=log⁡2(1/ε),εBE=(ε8L)2,\beta=\sum_{j=1}^d|\theta_j|+2(1+\log_2(2\kappa)),\qquad L=\log_2(1/\varepsilon),\qquad \varepsilon_{\rm BE}=\left(\frac{\varepsilon}{8L}\right)^2,β=j=1∑d​∣θj​∣+2(1+log2​(2κ)),L=log2​(1/ε),εBE​=(8Lε​)2,

where 0<ε<2−β0<\varepsilon<2^{-\beta}0<ε<2−β. The input ρ\rhoρ is an nnn-qubit trace-one density operator whose eigenvalues lie in [1/κ,1][1/\kappa,1][1/κ,1]. Each HjH_jHj​ is Hermitian with ∥Hj∥op≤1\|H_j\|_{\rm op}\le1∥Hj​∥op​≤1. Purified access is a unitary OρO_\rhoOρ​ on nρ+nn_\rho+nnρ​+n qubits preparing a purification of ρ\rhoρ, with the nρn_\rhonρ​ ancillary qubits first. Let UρU_\rhoUρ​ be the exact (1,n+nρ,0)(1,n+n_\rho,0)(1,n+nρ​,0) block-encoding supplied by the purification construction of Proposition 12. For each jjj, supplied UjU_jUj​ is a (1,a,εBE)(1,a,\varepsilon_{\rm BE})(1,a,εBE​) block-encoding of HjH_jHj​; ordinary, adjoint and controlled signal access are available.

There are universal constants Cρ,Cobs>0C_\rho,C_{\rm obs}>0Cρ​,Cobs​>0, a nonnegative integer ppp, and a universal threshold 0<ε0<10<\varepsilon_0<10<ε0​<1 such that, for every admissible public parameter choice with ε≤ε0\varepsilon\le\varepsilon_0ε≤ε0​, a QEsscher circuit can be selected before ρ,Hj,Oρ,Uj\rho,H_j,O_\rho,U_jρ,Hj​,Oρ​,Uj​. This circuit is the logarithm transformation, coefficient state-preparation pair, padded linear combination, and exponential transformation of Algorithm 1. It works for every admissible hidden input and oracle completion. With b=⌈log⁡2(d+1)⌉b=\lceil\log_2(d+1)\rceilb=⌈log2​(d+1)⌉ and aout=max⁡(a,n+nρ)+b+4a_{\rm out}=\max(a,n+n_\rho)+b+4aout​=max(a,n+nρ​)+b+4, its unitary UoutU_{\rm out}Uout​ satisfies

∥σ−(⟨0aout∣⊗In)Uout(∣0aout⟩⊗In)∥op≤ε,σ=exp⁡ ⁣(∑j=1dθjHj+log⁡2ρ)4eβ.\left\|\sigma-(\langle0^{a_{\rm out}}|\otimes I_n)U_{\rm out}(|0^{a_{\rm out}}\rangle\otimes I_n)\right\|_{\rm op}\le\varepsilon, \qquad \sigma=\frac{\exp\!\left(\sum_{j=1}^d\theta_jH_j+\log_2\rho\right)}{4e^\beta}.∥σ−(⟨0aout​∣⊗In​)Uout​(∣0aout​⟩⊗In​)∥op​≤ε,σ=4eβexp(∑j=1d​θj​Hj​+log2​ρ)​.

Its oracle counts, including ordinary, adjoint and controlled calls, obey

qρ≤CρκL2max⁡ ⁣(1,log⁡2(2+κL2))p,qj≤CobsL(j∈[d]).q_\rho\le C_\rho\kappa L^2\max\!\left(1,\log_2(2+\kappa L^2)\right)^p, \qquad q_j\le C_{\rm obs}L\quad(j\in[d]).qρ​≤Cρ​κL2max(1,log2​(2+κL2))p,qj​≤Cobs​L(j∈[d]).

The logarithm of a positive matrix is defined by applying log⁡2\log_2log2​ to its eigenvalues; exp⁡\expexp is the natural matrix exponential. The constants, exponent and threshold are independent of all public parameters, hidden matrices and oracle implementations.

This supplies the subnormalized transform as a block-encoding, useful as an operator primitive. The query count is for UρU_\rhoUρ​; each such call can be implemented with a constant number of purification-oracle calls. The actual nρn_\rhonρ​ is retained in the footprint; the source's nρ=poly⁡(n)n_\rho=\operatorname{poly}(n)nρ​=poly(n) is a family convention, and no gate-time conclusion is asserted.

Source corrections and limitation. Algorithm 1 and Step 3 print b=⌈log⁡2d⌉b=\lceil\log_2d\rceilb=⌈log2​d⌉, although their d+1d+1d+1 coefficients require b=⌈log⁡2(d+1)⌉b=\lceil\log_2(d+1)\rceilb=⌈log2​(d+1)⌉. The box prints the divisor eβe^\betaeβ; the statement uses proof Step 5's explicit 4eβ4e^\beta4eβ. The printed error schedule is retained. The claim that its numeral 8 ensures Eq. (III.2) has an unresolved quantitative degree-bound gap; accuracy remains the theorem's conclusion, without adding that bound as an assumption.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • The Quantum Esscher Transform, arXiv:2401.07561v2. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
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Quantum Information·Captain: Goku

Explicit decoders using fixed-point amplitude amplification based on QSVTResearch Paper

Motivation

Explicit decoders using fixed-point amplitude amplification based on QSVT establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let FAB→D\mathcal F^{AB\to D}FAB→D be any channel on finite registers of positive dimensions dA,dB,dDd_A,d_B,d_DdA​,dB​,dD​, with fixed computational bases. The registers R,R′R,R'R,R′ copy AAA, and B′B'B′ copies BBB, including their bases. Choose any Stinespring isometry V:AB→EDV:AB\to EDV:AB→ED and a compatible unitary UF:ABF→EDU_{\mathcal F}:ABF\to EDUF​:ABF→ED with V=UF∣0⟩FV=U_{\mathcal F}|0\rangle^FV=UF​∣0⟩F and dAdBdF=dEdDd_A d_B d_F=d_E d_DdA​dB​dF​=dE​dD​. Write F‾\overline{\mathcal F}F for the complementary channel derived from this same isometry, ΦAR\Phi^{AR}ΦAR for the normalized computational-basis maximally entangled state, and πX=IX/dX\pi^X=I_X/d_XπX=IX​/dX​. Define ωRE=F‾(ΦAR⊗πB)\omega^{RE}=\overline{\mathcal F}(\Phi^{AR}\otimes\pi^B)ωRE=F(ΦAR⊗πB) and let λmin⁡(ωRE)\lambda_{\min}(\omega^{RE})λmin​(ωRE) be its smallest strictly positive eigenvalue.

Suppose there is a density state τE\tau^EτE such that ∥ωRE−πR⊗τE∥1≤ε\|\omega^{RE}-\pi^R\otimes\tau^E\|_1\le\varepsilon∥ωRE−πR⊗τE∥1​≤ε. For every 0<δ<10<\delta<10<δ<1 and every odd positive integer ttt satisfying

t≥⌈16edDdBλmin⁡(ωRE)ln⁡2δ⌉,t\ge\left\lceil16e\sqrt{\frac{d_D}{d_B\lambda_{\min}(\omega^{RE})}}\ln\frac{2}{\delta}\right\rceil,t≥⌈16edB​λmin​(ωRE)dD​​​lnδ2​⌉,

there are phases ϕ1,…,ϕt∈(−π,π]\phi_1,\ldots,\phi_t\in(-\pi,\pi]ϕ1​,…,ϕt​∈(−π,π] for the explicit generalized Yoshida–Kitaev decoder Dt,ϕDB′→R′\mathcal D_{t,\phi}^{DB'\to R'}Dt,ϕDB′→R′​ of Eq. (44), with preprocessing (35) and the real two-projector QSVT (49)–(53), such that

Δ(Dt,ϕ∣F)=12∥ΦRR′−(idR⊗Dt,ϕ)(ωRDB′)∥1≤ε+δ,ωRDB′=FAB→D(ΦAR⊗ΦBB′).\Delta(\mathcal D_{t,\phi}\mid\mathcal F)=\frac12\left\|\Phi^{RR'}-(\mathrm{id}_R\otimes\mathcal D_{t,\phi})(\omega^{RDB'})\right\|_1\le\sqrt{\varepsilon}+\delta, \qquad \omega^{RDB'}=\mathcal F^{AB\to D}(\Phi^{AR}\otimes\Phi^{BB'}).Δ(Dt,ϕ​∣F)=21​​ΦRR′−(idR​⊗Dt,ϕ​)(ωRDB′)​1​≤ε​+δ,ωRDB′=FAB→D(ΦAR⊗ΦBB′).

The channel acts as the identity on the untouched reference RRR and shared register B′B'B′ in the expression for ωRDB′\omega^{RDB'}ωRDB′. The same choice of phases admits an exact circuit using arbitrary single- and two-qubit unitary gates with universal positive constants Cg,CaC_g,C_aCg​,Ca​ such that

gate count≤Cgt(C(UF)+log⁡2dD2dEdB),added ancilla qubits≤Calog⁡2dD2dEdB.\text{gate count}\le C_g t\left(\mathcal C(U_{\mathcal F})+\log_2\frac{d_D^2d_E}{d_B}\right), \qquad \text{added ancilla qubits}\le C_a\log_2\frac{d_D^2d_E}{d_B}.gate count≤Cg​t(C(UF​)+log2​dB​dD2​dE​​),added ancilla qubits≤Ca​log2​dB​dD2​dE​​.

Here the standing circuit model of Section 2.1 permits only polynomially many ancillary qubits. One polynomial allowance p∈N[X]p\in\mathbb N[X]p∈N[X] is chosen before all dimensions, channels and dilations. With q=⌈log⁡2(dEdD)⌉q=\lceil\log_2(d_Ed_D)\rceilq=⌈log2​(dE​dD​)⌉, Cp(UF)\mathcal C_p(U_{\mathcal F})Cp​(UF​) is the minimum exact gate count for the chosen dilation unitary within an added-ancilla budget p(q)p(q)p(q), including its input and output basis layout; the displayed C(UF)\mathcal C(U_{\mathcal F})C(UF​) denotes this cost under the common chosen allowance. Both constants are independent of the channel, dimensions, chosen dilation, errors and ttt. The decoder acts only on the receiver's DB′DB'DB′ systems and locally prepared ancillas. This supplies an explicit recovery circuit whenever decoupling holds, including unassisted communication (dB=1d_B=1dB​=1), exact decoupling (ε=0\varepsilon=0ε=0), and rank-deficient states.

Formalization Note Finite registers are embedded in ⌈log⁡2d⌉\lceil\log_2 d\rceil⌈log2​d⌉ qubits by the frozen finite-register embedding; no power-of-two dimension assumption is added. The full trace norm is used for decoupling and half that norm for recovery. The logarithm in the degree threshold is natural, as in the proof's Lambert-W estimate; qubit resource logarithms are base two. The compatible dimension identity makes the resource logarithm nonnegative. When it vanishes, the recovered register is one-dimensional and discarding the input uses zero gates and added ancillas.

Target

Theorem 4, Eqs. (45)–(48)

Let FAB→D\mathcal F^{AB\to D}FAB→D be any channel on finite registers of positive dimensions dA,dB,dDd_A,d_B,d_DdA​,dB​,dD​, with fixed computational bases. The registers R,R′R,R'R,R′ copy AAA, and B′B'B′ copies BBB, including their bases. Choose any Stinespring isometry V:AB→EDV:AB\to EDV:AB→ED and a compatible unitary UF:ABF→EDU_{\mathcal F}:ABF\to EDUF​:ABF→ED with V=UF∣0⟩FV=U_{\mathcal F}|0\rangle^FV=UF​∣0⟩F and dAdBdF=dEdDd_A d_B d_F=d_E d_DdA​dB​dF​=dE​dD​. Write F‾\overline{\mathcal F}F for the complementary channel derived from this same isometry, ΦAR\Phi^{AR}ΦAR for the normalized computational-basis maximally entangled state, and πX=IX/dX\pi^X=I_X/d_XπX=IX​/dX​. Define ωRE=F‾(ΦAR⊗πB)\omega^{RE}=\overline{\mathcal F}(\Phi^{AR}\otimes\pi^B)ωRE=F(ΦAR⊗πB) and let λmin⁡(ωRE)\lambda_{\min}(\omega^{RE})λmin​(ωRE) be its smallest strictly positive eigenvalue.

Suppose there is a density state τE\tau^EτE such that ∥ωRE−πR⊗τE∥1≤ε\|\omega^{RE}-\pi^R\otimes\tau^E\|_1\le\varepsilon∥ωRE−πR⊗τE∥1​≤ε. For every 0<δ<10<\delta<10<δ<1 and every odd positive integer ttt satisfying

t≥⌈16edDdBλmin⁡(ωRE)ln⁡2δ⌉,t\ge\left\lceil16e\sqrt{\frac{d_D}{d_B\lambda_{\min}(\omega^{RE})}}\ln\frac{2}{\delta}\right\rceil,t≥⌈16edB​λmin​(ωRE)dD​​​lnδ2​⌉,

there are phases ϕ1,…,ϕt∈(−π,π]\phi_1,\ldots,\phi_t\in(-\pi,\pi]ϕ1​,…,ϕt​∈(−π,π] for the explicit generalized Yoshida–Kitaev decoder Dt,ϕDB′→R′\mathcal D_{t,\phi}^{DB'\to R'}Dt,ϕDB′→R′​ of Eq. (44), with preprocessing (35) and the real two-projector QSVT (49)–(53), such that

Δ(Dt,ϕ∣F)=12∥ΦRR′−(idR⊗Dt,ϕ)(ωRDB′)∥1≤ε+δ,ωRDB′=FAB→D(ΦAR⊗ΦBB′).\Delta(\mathcal D_{t,\phi}\mid\mathcal F)=\frac12\left\|\Phi^{RR'}-(\mathrm{id}_R\otimes\mathcal D_{t,\phi})(\omega^{RDB'})\right\|_1\le\sqrt{\varepsilon}+\delta, \qquad \omega^{RDB'}=\mathcal F^{AB\to D}(\Phi^{AR}\otimes\Phi^{BB'}).Δ(Dt,ϕ​∣F)=21​​ΦRR′−(idR​⊗Dt,ϕ​)(ωRDB′)​1​≤ε​+δ,ωRDB′=FAB→D(ΦAR⊗ΦBB′).

The channel acts as the identity on the untouched reference RRR and shared register B′B'B′ in the expression for ωRDB′\omega^{RDB'}ωRDB′. The same choice of phases admits an exact circuit using arbitrary single- and two-qubit unitary gates with universal positive constants Cg,CaC_g,C_aCg​,Ca​ such that

gate count≤Cgt(C(UF)+log⁡2dD2dEdB),added ancilla qubits≤Calog⁡2dD2dEdB.\text{gate count}\le C_g t\left(\mathcal C(U_{\mathcal F})+\log_2\frac{d_D^2d_E}{d_B}\right), \qquad \text{added ancilla qubits}\le C_a\log_2\frac{d_D^2d_E}{d_B}.gate count≤Cg​t(C(UF​)+log2​dB​dD2​dE​​),added ancilla qubits≤Ca​log2​dB​dD2​dE​​.

Here the standing circuit model of Section 2.1 permits only polynomially many ancillary qubits. One polynomial allowance p∈N[X]p\in\mathbb N[X]p∈N[X] is chosen before all dimensions, channels and dilations. With q=⌈log⁡2(dEdD)⌉q=\lceil\log_2(d_Ed_D)\rceilq=⌈log2​(dE​dD​)⌉, Cp(UF)\mathcal C_p(U_{\mathcal F})Cp​(UF​) is the minimum exact gate count for the chosen dilation unitary within an added-ancilla budget p(q)p(q)p(q), including its input and output basis layout; the displayed C(UF)\mathcal C(U_{\mathcal F})C(UF​) denotes this cost under the common chosen allowance. Both constants are independent of the channel, dimensions, chosen dilation, errors and ttt. The decoder acts only on the receiver's DB′DB'DB′ systems and locally prepared ancillas. This supplies an explicit recovery circuit whenever decoupling holds, including unassisted communication (dB=1d_B=1dB​=1), exact decoupling (ε=0\varepsilon=0ε=0), and rank-deficient states.

Formalization Note Finite registers are embedded in ⌈log⁡2d⌉\lceil\log_2 d\rceil⌈log2​d⌉ qubits by the frozen finite-register embedding; no power-of-two dimension assumption is added. The full trace norm is used for decoupling and half that norm for recovery. The logarithm in the degree threshold is natural, as in the proof's Lambert-W estimate; qubit resource logarithms are base two. The compatible dimension identity makes the resource logarithm nonnegative. When it vanishes, the recovered register is one-dimensional and discarding the input uses zero gates and added ancillas.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Explicit decoders using fixed-point amplitude amplification based on QSVT, arXiv:2405.06051v6. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Information·Captain: Goku

Amplitude Estimation from Quantum Signal ProcessingResearch Paper

Motivation

Amplitude Estimation from Quantum Signal Processing establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let a∈[0,1]a\in[0,1]a∈[0,1] be an unknown amplitude in the completed two-dimensional Grover space. Choose an orthonormal pair ∣Π⟩,∣Π⊥⟩|\Pi\rangle,|\Pi^\perp\rangle∣Π⟩,∣Π⊥⟩, set aˉ=1−a2\bar a=\sqrt{1-a^2}aˉ=1−a2​, and write ∣ψ⟩=a∣Π⟩+aˉ∣Π⊥⟩|\psi\rangle=a|\Pi\rangle+\bar a|\Pi^\perp\rangle∣ψ⟩=a∣Π⟩+aˉ∣Π⊥⟩ and ∣ψ⊥⟩=aˉ∣Π⟩−a∣Π⊥⟩|\psi^\perp\rangle=\bar a|\Pi\rangle-a|\Pi^\perp\rangle∣ψ⊥⟩=aˉ∣Π⟩−a∣Π⊥⟩. The endpoint states are understood as rays. Define Zψ=∣ψ⟩⟨ψ∣−∣ψ⊥⟩⟨ψ⊥∣Z_\psi=|\psi\rangle\langle\psi|-|\psi^\perp\rangle\langle\psi^\perp|Zψ​=∣ψ⟩⟨ψ∣−∣ψ⊥⟩⟨ψ⊥∣ and ZΠ=∣Π⟩⟨Π∣−∣Π⊥⟩⟨Π⊥∣Z_\Pi=|\Pi\rangle\langle\Pi|-|\Pi^\perp\rangle\langle\Pi^\perp|ZΠ​=∣Π⟩⟨Π∣−∣Π⊥⟩⟨Π⊥∣. A complex polynomial PPP is Pellian if there is a polynomial QQQ of the opposite fixed parity such that ∣P(x)∣2+(1−x2)∣Q(x)∣2=1|P(x)|^2+(1-x^2)|Q(x)|^2=1∣P(x)∣2+(1−x2)∣Q(x)∣2=1 for every x∈[−1,1]x\in[-1,1]x∈[−1,1]. A real polynomial is semi-Pellian if it is the coefficientwise real part of a Pellian polynomial.

There is an absolute constant C>0C>0C>0 such that, for every Pellian or semi-Pellian polynomial PPP, an oracle instrument can be chosen independently of aaa and of the orthonormal basis. Given one copy of any of the four states and its known classical label, the instrument outputs a bit bPb_PbP​ satisfying

Pr⁡[bP=1]=∣P(a)∣2.\Pr[b_P=1]=|P(a)|^2.Pr[bP​=1]=∣P(a)∣2.

It also returns a classical label LLL for a retained signal state. For each joint outcome (bP,L)(b_P,L)(bP​,L) of probability ppp, the unnormalized signal density matrix is exactly p∣L⟩⟨L∣p|L\rangle\langle L|p∣L⟩⟨L∣, with L∈{ψ,ψ⊥,Π,Π⊥}L\in\{\psi,\psi^\perp,\Pi,\Pi^\perp\}L∈{ψ,ψ⊥,Π,Π⊥}. This includes both sampled-bit outcomes. The total number of oracle calls, including the oracle-assisted final basis measurement, is at most C(deg⁡P+1)C(\deg P+1)C(degP+1) for every input label. Pellian sampling uses arbitrary-angle rotations eiϕZψ,eiϕZΠe^{i\phi Z_\psi},e^{i\phi Z_\Pi}eiϕZψ​,eiϕZΠ​, with the controlled measurement access used in the proof. Semi-Pellian sampling uses the distinct primitives ∣0⟩⟨0∣⊗eiϕZ+∣1⟩⟨1∣⊗e−iϕZ|0\rangle\langle0|\otimes e^{i\phi Z}+|1\rangle\langle1|\otimes e^{-i\phi Z}∣0⟩⟨0∣⊗eiϕZ+∣1⟩⟨1∣⊗e−iϕZ for each basis. Ancilla preparation and known ancilla gates are free in this query model.

The retained-state guarantee allows successive polynomial samples from the same signal system, without requiring that each invocation restore the original state.

Formalization Note The completed Grover-space model includes a=0,1a=0,1a=0,1 and uses density matrices to ignore global phase. The asymptotic query claim is expressed with a uniform additive degree-zero allowance. Controlled access for the Pellian basis measurement is the operational convention of the source's proof; it is not derived from a strictly uncontrolled black box.

Target

§1.4, Theorem 6, equation (39)

Let a∈[0,1]a\in[0,1]a∈[0,1] be an unknown amplitude in the completed two-dimensional Grover space. Choose an orthonormal pair ∣Π⟩,∣Π⊥⟩|\Pi\rangle,|\Pi^\perp\rangle∣Π⟩,∣Π⊥⟩, set aˉ=1−a2\bar a=\sqrt{1-a^2}aˉ=1−a2​, and write ∣ψ⟩=a∣Π⟩+aˉ∣Π⊥⟩|\psi\rangle=a|\Pi\rangle+\bar a|\Pi^\perp\rangle∣ψ⟩=a∣Π⟩+aˉ∣Π⊥⟩ and ∣ψ⊥⟩=aˉ∣Π⟩−a∣Π⊥⟩|\psi^\perp\rangle=\bar a|\Pi\rangle-a|\Pi^\perp\rangle∣ψ⊥⟩=aˉ∣Π⟩−a∣Π⊥⟩. The endpoint states are understood as rays. Define Zψ=∣ψ⟩⟨ψ∣−∣ψ⊥⟩⟨ψ⊥∣Z_\psi=|\psi\rangle\langle\psi|-|\psi^\perp\rangle\langle\psi^\perp|Zψ​=∣ψ⟩⟨ψ∣−∣ψ⊥⟩⟨ψ⊥∣ and ZΠ=∣Π⟩⟨Π∣−∣Π⊥⟩⟨Π⊥∣Z_\Pi=|\Pi\rangle\langle\Pi|-|\Pi^\perp\rangle\langle\Pi^\perp|ZΠ​=∣Π⟩⟨Π∣−∣Π⊥⟩⟨Π⊥∣. A complex polynomial PPP is Pellian if there is a polynomial QQQ of the opposite fixed parity such that ∣P(x)∣2+(1−x2)∣Q(x)∣2=1|P(x)|^2+(1-x^2)|Q(x)|^2=1∣P(x)∣2+(1−x2)∣Q(x)∣2=1 for every x∈[−1,1]x\in[-1,1]x∈[−1,1]. A real polynomial is semi-Pellian if it is the coefficientwise real part of a Pellian polynomial.

There is an absolute constant C>0C>0C>0 such that, for every Pellian or semi-Pellian polynomial PPP, an oracle instrument can be chosen independently of aaa and of the orthonormal basis. Given one copy of any of the four states and its known classical label, the instrument outputs a bit bPb_PbP​ satisfying

Pr⁡[bP=1]=∣P(a)∣2.\Pr[b_P=1]=|P(a)|^2.Pr[bP​=1]=∣P(a)∣2.

It also returns a classical label LLL for a retained signal state. For each joint outcome (bP,L)(b_P,L)(bP​,L) of probability ppp, the unnormalized signal density matrix is exactly p∣L⟩⟨L∣p|L\rangle\langle L|p∣L⟩⟨L∣, with L∈{ψ,ψ⊥,Π,Π⊥}L\in\{\psi,\psi^\perp,\Pi,\Pi^\perp\}L∈{ψ,ψ⊥,Π,Π⊥}. This includes both sampled-bit outcomes. The total number of oracle calls, including the oracle-assisted final basis measurement, is at most C(deg⁡P+1)C(\deg P+1)C(degP+1) for every input label. Pellian sampling uses arbitrary-angle rotations eiϕZψ,eiϕZΠe^{i\phi Z_\psi},e^{i\phi Z_\Pi}eiϕZψ​,eiϕZΠ​, with the controlled measurement access used in the proof. Semi-Pellian sampling uses the distinct primitives ∣0⟩⟨0∣⊗eiϕZ+∣1⟩⟨1∣⊗e−iϕZ|0\rangle\langle0|\otimes e^{i\phi Z}+|1\rangle\langle1|\otimes e^{-i\phi Z}∣0⟩⟨0∣⊗eiϕZ+∣1⟩⟨1∣⊗e−iϕZ for each basis. Ancilla preparation and known ancilla gates are free in this query model.

The retained-state guarantee allows successive polynomial samples from the same signal system, without requiring that each invocation restore the original state.

Formalization Note The completed Grover-space model includes a=0,1a=0,1a=0,1 and uses density matrices to ignore global phase. The asymptotic query claim is expressed with a uniform additive degree-zero allowance. Controlled access for the Pellian basis measurement is the operational convention of the source's proof; it is not derived from a strictly uncontrolled black box.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Amplitude Estimation from Quantum Signal Processing, arXiv:2207.08628v3. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Error CorrectionQuantum Information·Captain: Goku

Single-shot decoding of good quantum LDPC codesResearch Paper

Motivation

Single-shot decoding of good quantum LDPC codes establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Fix code parameters ρ,dr,κ∈(0,1)\rho,d_r,\kappa\in(0,1)ρ,dr​,κ∈(0,1) and decoder parameters 0<2δ<ε<10<2\delta<\varepsilon<10<2δ<ε<1. For all sufficiently large degrees Δ\DeltaΔ (with the threshold depending only on these fixed parameters), let GGG be a finite group with symmetric generating sets A,BA,BA,B of size Δ\DeltaΔ, whose left and right Cayley graphs are Ramanujan in the paper's sense: their second largest adjacency eigenvalue is at most 2Δ−12\sqrt{\Delta-1}2Δ−1​. Let the binary local codes CA,CBC_A,C_BCA​,CB​ have exact rates ρ,1−ρ\rho,1-\rhoρ,1−ρ, respectively. Each of CA,CB,CA⊥,CB⊥C_A,C_B,C_A^\perp,C_B^\perpCA​,CB​,CA⊥​,CB⊥​ has distance at least drΔd_r\Deltadr​Δ, and both dual tensor codes CA⊞CBC_A\boxplus C_BCA​⊞CB​ and CA⊥⊞CB⊥C_A^\perp\boxplus C_B^\perpCA⊥​⊞CB⊥​ are κ\kappaκ-product-expanding.

Construct the quadripartite quantum Tanner code on Q=G×A×BQ=G\times A\times BQ=G×A×B, with n=∣G∣Δ2n=|G|\Delta^2n=∣G∣Δ2 qubits, X checks from CA⊗CBC_A\otimes C_BCA​⊗CB​ at V00∪V11V_{00}\cup V_{11}V00​∪V11​ and Z checks from CA⊥⊗CB⊥C_A^\perp\otimes C_B^\perpCA⊥​⊗CB⊥​ at V01∪V10V_{01}\cup V_{10}V01​∪V10​. Let ddd be its actual CSS distance. Let e∈F2Qe\in\mathbb F_2^Qe∈F2Q​ be an X error and DDD a binary error on the vertex-labelled Z checks. Write ∣e∣R=min⁡s∈CX⊥∣e+s∣|e|_R=\min_{s\in C_X^\perp}|e+s|∣e∣R​=mins∈CX⊥​​∣e+s∣ and let ∣D∣V|D|_V∣D∣V​ count vertices with at least one nonzero syndrome-error bit. Define

Aε=24κΔ(1−ε),Bε=3Δκ(1−ε),Cδ=dr2δ3κ212Δ2,c1=ε−2δε(1−δ),c2=2ε.A_\varepsilon=\frac{24}{\kappa\Delta(1-\varepsilon)},\quad B_\varepsilon=\frac{3\Delta}{\kappa(1-\varepsilon)},\quad C_\delta=\frac{d_r^2\delta^3\kappa}{2^{12}\Delta^2},\quad c_1=\frac{\varepsilon-2\delta}{\varepsilon(1-\delta)},\quad c_2=\frac2\varepsilon.Aε​=κΔ(1−ε)24​,Bε​=κ(1−ε)3Δ​,Cδ​=212Δ2dr2​δ3κ​,c1​=ε(1−δ)ε−2δ​,c2​=ε2​.

If

Aε∣e∣R+Bε∣D∣V≤min⁡(Cδn,d/Δ),A_\varepsilon|e|_R+B_\varepsilon|D|_V\le\min(C_\delta n,d/\Delta),Aε​∣e∣R​+Bε​∣D∣V​≤min(Cδ​n,d/Δ),

then Algorithm 1, receiving only σ~=HZe+D\widetilde\sigma=H_Ze+Dσ=HZ​e+D and parameter ε\varepsilonε, terminates and every lawful output f^\widehat ff​ satisfies

∣e+f^∣R≤(1+2c2κc1)Δ2∣D∣V.|e+\widehat f|_R\le\left(1+\frac{2c_2}{\kappa c_1}\right)\Delta^2|D|_V.∣e+f​∣R​≤(1+κc1​2c2​​)Δ2∣D∣V​.

Local minimum-weight choices are fixed consistently before the input; infeasible local syndromes use the zero fallback. Algorithm 2 starts with zero accumulators, uses the stated weight-decrease test and minimum column/row decomposition, and halts only at zero mismatch or when no permitted move exists. Algorithm 1 returns ∑v∈V01ε~v+C^1+R^0\sum_{v\in V_{01}}\widetilde\varepsilon_v+\widehat C_1+\widehat R_0∑v∈V01​​εv​+C1​+R0​.

This is the quantitative adversarial single-shot guarantee for the sequential Tanner decoder. With D=0D=0D=0, the residual is a stabilizer, rather than necessarily the zero vector.

Formalization Note The printed theorem leaves decoder domains implicit; the range above is inherited from pp.14 and 22. The distance is an extended natural minimum; when both logical-error sets are empty it is infinite, and the threshold uses only CδnC_\delta nCδ​n. Termination is represented by existence of a terminal execution together with the bound for every lawful terminal execution. No stochastic residual support law is asserted.

Target

Theorem 4.17 (Main Theorem for the Sequential Decoder)

Fix code parameters ρ,dr,κ∈(0,1)\rho,d_r,\kappa\in(0,1)ρ,dr​,κ∈(0,1) and decoder parameters 0<2δ<ε<10<2\delta<\varepsilon<10<2δ<ε<1. For all sufficiently large degrees Δ\DeltaΔ (with the threshold depending only on these fixed parameters), let GGG be a finite group with symmetric generating sets A,BA,BA,B of size Δ\DeltaΔ, whose left and right Cayley graphs are Ramanujan in the paper's sense: their second largest adjacency eigenvalue is at most 2Δ−12\sqrt{\Delta-1}2Δ−1​. Let the binary local codes CA,CBC_A,C_BCA​,CB​ have exact rates ρ,1−ρ\rho,1-\rhoρ,1−ρ, respectively. Each of CA,CB,CA⊥,CB⊥C_A,C_B,C_A^\perp,C_B^\perpCA​,CB​,CA⊥​,CB⊥​ has distance at least drΔd_r\Deltadr​Δ, and both dual tensor codes CA⊞CBC_A\boxplus C_BCA​⊞CB​ and CA⊥⊞CB⊥C_A^\perp\boxplus C_B^\perpCA⊥​⊞CB⊥​ are κ\kappaκ-product-expanding.

Construct the quadripartite quantum Tanner code on Q=G×A×BQ=G\times A\times BQ=G×A×B, with n=∣G∣Δ2n=|G|\Delta^2n=∣G∣Δ2 qubits, X checks from CA⊗CBC_A\otimes C_BCA​⊗CB​ at V00∪V11V_{00}\cup V_{11}V00​∪V11​ and Z checks from CA⊥⊗CB⊥C_A^\perp\otimes C_B^\perpCA⊥​⊗CB⊥​ at V01∪V10V_{01}\cup V_{10}V01​∪V10​. Let ddd be its actual CSS distance. Let e∈F2Qe\in\mathbb F_2^Qe∈F2Q​ be an X error and DDD a binary error on the vertex-labelled Z checks. Write ∣e∣R=min⁡s∈CX⊥∣e+s∣|e|_R=\min_{s\in C_X^\perp}|e+s|∣e∣R​=mins∈CX⊥​​∣e+s∣ and let ∣D∣V|D|_V∣D∣V​ count vertices with at least one nonzero syndrome-error bit. Define

Aε=24κΔ(1−ε),Bε=3Δκ(1−ε),Cδ=dr2δ3κ212Δ2,c1=ε−2δε(1−δ),c2=2ε.A_\varepsilon=\frac{24}{\kappa\Delta(1-\varepsilon)},\quad B_\varepsilon=\frac{3\Delta}{\kappa(1-\varepsilon)},\quad C_\delta=\frac{d_r^2\delta^3\kappa}{2^{12}\Delta^2},\quad c_1=\frac{\varepsilon-2\delta}{\varepsilon(1-\delta)},\quad c_2=\frac2\varepsilon.Aε​=κΔ(1−ε)24​,Bε​=κ(1−ε)3Δ​,Cδ​=212Δ2dr2​δ3κ​,c1​=ε(1−δ)ε−2δ​,c2​=ε2​.

If

Aε∣e∣R+Bε∣D∣V≤min⁡(Cδn,d/Δ),A_\varepsilon|e|_R+B_\varepsilon|D|_V\le\min(C_\delta n,d/\Delta),Aε​∣e∣R​+Bε​∣D∣V​≤min(Cδ​n,d/Δ),

then Algorithm 1, receiving only σ~=HZe+D\widetilde\sigma=H_Ze+Dσ=HZ​e+D and parameter ε\varepsilonε, terminates and every lawful output f^\widehat ff​ satisfies

∣e+f^∣R≤(1+2c2κc1)Δ2∣D∣V.|e+\widehat f|_R\le\left(1+\frac{2c_2}{\kappa c_1}\right)\Delta^2|D|_V.∣e+f​∣R​≤(1+κc1​2c2​​)Δ2∣D∣V​.

Local minimum-weight choices are fixed consistently before the input; infeasible local syndromes use the zero fallback. Algorithm 2 starts with zero accumulators, uses the stated weight-decrease test and minimum column/row decomposition, and halts only at zero mismatch or when no permitted move exists. Algorithm 1 returns ∑v∈V01ε~v+C^1+R^0\sum_{v\in V_{01}}\widetilde\varepsilon_v+\widehat C_1+\widehat R_0∑v∈V01​​εv​+C1​+R0​.

This is the quantitative adversarial single-shot guarantee for the sequential Tanner decoder. With D=0D=0D=0, the residual is a stabilizer, rather than necessarily the zero vector.

Formalization Note The printed theorem leaves decoder domains implicit; the range above is inherited from pp.14 and 22. The distance is an extended natural minimum; when both logical-error sets are empty it is infinite, and the threshold uses only CδnC_\delta nCδ​n. Termination is represented by existence of a terminal execution together with the bound for every lawful terminal execution. No stochastic residual support law is asserted.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Single-shot decoding of good quantum LDPC codes, arXiv:2306.12470v2. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Machine LearningQuantum Information·Captain: Goku

Fast Estimation of Sparse Quantum NoiseResearch Paper

Motivation

Fast Estimation of Sparse Quantum Noise establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Fix a sparsity exponent 0<δ<1/20<\delta<1/20<δ<1/2. There are positive constants C,c,βC,c,\betaC,c,β and a threshold n0≥1n_0\ge1n0​≥1, depending only on this fixed exponent and public design/code choices, and a public construction of the subsampling and peeling protocol for every n≥n0n\ge n_0n≥n0​ and integer s=4δns=4^{\delta n}s=4δn.

The labels of the N=4nN=4^nN=4n phase-free nnn-qubit Paulis are a=(ax,az)∈F22na=(a_x,a_z)\in\mathbb F_2^{2n}a=(ax​,az​)∈F22n​. Let KKK be uniform among the size-sss subsets of these labels. For each possible KKK, assign arbitrary nonnegative rates p(K)p^{(K)}p(K) with total mass one, support exactly KKK, and pa(K)≥ϵ0>0p^{(K)}_a\ge\epsilon_0>0pa(K)​≥ϵ0​>0 on KKK. This assignment is independent of the protocol's public randomness and observation noise. The associated channel is E(ρ)=∑apaPaρPa\mathcal E(\rho)=\sum_a p_aP_a\rho P_aE(ρ)=∑a​pa​Pa​ρPa​, and its eigenvalues are

λa=∑b(−1)ax⋅bz+az⋅bxpb.\lambda_a=\sum_b(-1)^{a_x\cdot b_z+a_z\cdot b_x}p_b.λa​=b∑​(−1)ax​⋅bz​+az​⋅bx​pb​.

The observed eigenvalue vector has independent centered Gaussian errors of variance ξ2\xi^2ξ2, with ξ≥0\xi\ge0ξ≥0, independent of the support and the public design. Repeated reads use the same indexed observation and are counted as queries.

The construction chooses B=2bB=2^bB=2b bins with s≤B≤Css\le B\le Css≤B≤Cs, constantly many subsampling groups, and P1,P2=Θ(n)P_1,P_2=\Theta(n)P1​,P2​=Θ(n) offsets. Random offsets and binary hash matrices are sampled independently and uniformly before the hidden input. Coded offsets use a full-rank binary linear code with positive constant relative distance and a public, query-free, linear-time decoder. The decoder's realization, correction property and time bound are conclusions of the construction. Assume

ξ2≤min⁡ ⁣(Bs2,1),ϵ0≥2ξB.\xi^2\le\min\!\left(\frac{B}{s^2},1\right), \qquad \epsilon_0\ge\frac{2\xi}{\sqrt B}.ξ2≤min(s2B​,1),ϵ0​≥B​2ξ​.

Algorithms 2–4 produce a list of distinct labels with support exactly KKK and estimated rates p^\widehat pp​, zero off the reported support, satisfying

Pr⁡ ⁣[supp⁡(p^)=K and ∥p^−p∥∞≤2ξB]≥1−e−cn.\Pr\!\left[ \operatorname{supp}(\widehat p)=K \ \text{and}\ \|\widehat p-p\|_\infty\le\frac{2\xi}{\sqrt B} \right]\ge1-e^{-cn}.Pr[supp(p​)=K and ∥p​−p∥∞​≤B​2ξ​]≥1−e−cn.

The probability averages over the uniform support, public design, Gaussian observations, and any internal decoder randomness. Every execution uses at most CsnCsnCsn eigenvalue reads and Csn2Csn^2Csn2 classical arithmetic/indexing instructions. The computed conditional success probabilities are measurable.

This result recovers both the locations and values of sparse Pauli errors from noisy eigenvalues. It does not assert a quantum measurement sample complexity.

Formalization Note The frozen, independently reviewed program composition is used directly. It separates the ordinary bbb-bit WHT from the symplectic 2n2n2n-bit label pairing, resolves the printed dimensional inconsistencies as approved in the definition review, and retires peeled bins according to the graph description. The theorem does not assume successful bin detection, favorable graph events, accuracy, runtime, or independence of overlapping bin errors.

Target

Theorem 1; Assumptions 1, Algorithms 2–4

Fix a sparsity exponent 0<δ<1/20<\delta<1/20<δ<1/2. There are positive constants C,c,βC,c,\betaC,c,β and a threshold n0≥1n_0\ge1n0​≥1, depending only on this fixed exponent and public design/code choices, and a public construction of the subsampling and peeling protocol for every n≥n0n\ge n_0n≥n0​ and integer s=4δns=4^{\delta n}s=4δn.

The labels of the N=4nN=4^nN=4n phase-free nnn-qubit Paulis are a=(ax,az)∈F22na=(a_x,a_z)\in\mathbb F_2^{2n}a=(ax​,az​)∈F22n​. Let KKK be uniform among the size-sss subsets of these labels. For each possible KKK, assign arbitrary nonnegative rates p(K)p^{(K)}p(K) with total mass one, support exactly KKK, and pa(K)≥ϵ0>0p^{(K)}_a\ge\epsilon_0>0pa(K)​≥ϵ0​>0 on KKK. This assignment is independent of the protocol's public randomness and observation noise. The associated channel is E(ρ)=∑apaPaρPa\mathcal E(\rho)=\sum_a p_aP_a\rho P_aE(ρ)=∑a​pa​Pa​ρPa​, and its eigenvalues are

λa=∑b(−1)ax⋅bz+az⋅bxpb.\lambda_a=\sum_b(-1)^{a_x\cdot b_z+a_z\cdot b_x}p_b.λa​=b∑​(−1)ax​⋅bz​+az​⋅bx​pb​.

The observed eigenvalue vector has independent centered Gaussian errors of variance ξ2\xi^2ξ2, with ξ≥0\xi\ge0ξ≥0, independent of the support and the public design. Repeated reads use the same indexed observation and are counted as queries.

The construction chooses B=2bB=2^bB=2b bins with s≤B≤Css\le B\le Css≤B≤Cs, constantly many subsampling groups, and P1,P2=Θ(n)P_1,P_2=\Theta(n)P1​,P2​=Θ(n) offsets. Random offsets and binary hash matrices are sampled independently and uniformly before the hidden input. Coded offsets use a full-rank binary linear code with positive constant relative distance and a public, query-free, linear-time decoder. The decoder's realization, correction property and time bound are conclusions of the construction. Assume

ξ2≤min⁡ ⁣(Bs2,1),ϵ0≥2ξB.\xi^2\le\min\!\left(\frac{B}{s^2},1\right), \qquad \epsilon_0\ge\frac{2\xi}{\sqrt B}.ξ2≤min(s2B​,1),ϵ0​≥B​2ξ​.

Algorithms 2–4 produce a list of distinct labels with support exactly KKK and estimated rates p^\widehat pp​, zero off the reported support, satisfying

Pr⁡ ⁣[supp⁡(p^)=K and ∥p^−p∥∞≤2ξB]≥1−e−cn.\Pr\!\left[ \operatorname{supp}(\widehat p)=K \ \text{and}\ \|\widehat p-p\|_\infty\le\frac{2\xi}{\sqrt B} \right]\ge1-e^{-cn}.Pr[supp(p​)=K and ∥p​−p∥∞​≤B​2ξ​]≥1−e−cn.

The probability averages over the uniform support, public design, Gaussian observations, and any internal decoder randomness. Every execution uses at most CsnCsnCsn eigenvalue reads and Csn2Csn^2Csn2 classical arithmetic/indexing instructions. The computed conditional success probabilities are measurable.

This result recovers both the locations and values of sparse Pauli errors from noisy eigenvalues. It does not assert a quantum measurement sample complexity.

Formalization Note The frozen, independently reviewed program composition is used directly. It separates the ordinary bbb-bit WHT from the symplectic 2n2n2n-bit label pairing, resolves the printed dimensional inconsistencies as approved in the definition review, and retires peeled bins according to the graph description. The theorem does not assume successful bin detection, favorable graph events, accuracy, runtime, or independence of overlapping bin errors.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Fast Estimation of Sparse Quantum Noise, arXiv:2007.07901v2. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Machine LearningQuantum Information·Captain: Goku

Provably efficient machine learning for quantum many-body problemsResearch Paper

Motivation

Provably efficient machine learning for quantum many-body problems establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Fix a finite spatial dimension ddd, bounds on the number and geometric radius of sites in each Hamiltonian term, a local-term density bound bd+cdrdb_d+c_dr^dbd​+cd​rd, a spectral gap γ>0\gamma>0γ>0, an observable locality bound qqq, and a confidence parameter δ∈(0,1)\delta\in(0,1)δ∈(0,1). Consider nnn-qubit Hamiltonians H(x)=∑jhj(x)H(x)=\sum_j h_j(x)H(x)=∑j​hj​(x), smoothly parametrized by x∈[−1,1]mx\in[-1,1]^mx∈[−1,1]m. Each term is Hermitian, obeys ∥hj(x)∥∞≤1\|h_j(x)\|_\infty\le1∥hj​(x)∥∞​≤1, and has directional derivative of operator norm at most one in every Euclidean unit parameter direction. These properties hold throughout the cube; smoothness at its boundary uses a local smooth extension. Every Hamiltonian has an excited energy and a gap at least γ\gammaγ above its entire ground eigenspace. Let ρ(x)\rho(x)ρ(x) be the normalized projector onto that eigenspace, allowing degeneracy.

For a fixed Hermitian observable O=∑i=1LOiO=\sum_{i=1}^L O_iO=∑i=1L​Oi​, each term supported on at most qqq qubits (not necessarily neighboring), choose a norm budget B≥1B\ge1B≥1 satisfying ∑i∥Oi∥∞≤B\sum_i\|O_i\|_\infty\le B∑i​∥Oi​∥∞​≤B. A smaller norm budget may be replaced by one. There are uniform positive constants, depending only on the fixed physical bounds, qqq, and δ\deltaδ, such that for every fixed mean-squared error tolerance ε∈(0,1]\varepsilon\in(0,1]ε∈(0,1] and all sufficiently large mmm, public sample counts, cutoffs, and actual classical arithmetic/RAM programs can be selected before the unknown Hamiltonian family, training draw, observable entries, and test parameter. The training set consists of NNN independent uniform parameter draws, with one fresh-copy randomized Pauli snapshot SℓS_\ellSℓ​ at each point. Pauli axes are independently uniform; the joint measurement outcomes obey the Born law.

The named predictor is

σ^N(x)=1N∑ℓ=1NκΛ(x,xℓ)Sℓ,κΛ(x,y)=∑k∈Zm∥k∥2≤Λcos⁡ ⁣(πk⋅(x−y)).\widehat{\sigma}_N(x)=\frac1N\sum_{\ell=1}^N\kappa_\Lambda(x,x_\ell)S_\ell,\qquad \kappa_\Lambda(x,y)=\sum_{\substack{k\in\mathbb Z^m\\\|k\|_2\le\Lambda}} \cos\!\bigl(\pi k\cdot(x-y)\bigr).σN​(x)=N1​ℓ=1∑N​κΛ​(x,xℓ​)Sℓ​,κΛ​(x,y)=k∈Zm∥k∥2​≤Λ​∑​cos(πk⋅(x−y)).

For each observable fixed before the training draw,

Pr⁡T ⁣[Ex∼Unif[−1,1]m∣tr⁡ ⁣(Oσ^N(x))−tr⁡ ⁣(Oρ(x))∣2≤ε]≥1−δ,\Pr_{\mathcal T}\!\left[ \mathbb E_{x\sim\mathrm{Unif}[-1,1]^m} \left|\operatorname{tr}\!\left(O\widehat{\sigma}_N(x)\right) -\operatorname{tr}\!\left(O\rho(x)\right)\right|^2 \le\varepsilon\right]\ge1-\delta,TPr​[Ex∼Unif[−1,1]m​∣tr(OσN​(x))−tr(Oρ(x))∣2≤ε]≥1−δ,

with N≤CB2mCB2/εN\le C B^2m^{C B^2/\varepsilon}N≤CB2mCB2/ε and computed classical training and prediction work O((n+L)B2mO(B2/ε))O((n+L)B^2m^{O(B^2/\varepsilon)})O((n+L)B2mO(B2/ε)). The compact representation stores mNmNmN real parameter words and nNnNnN six-valued labels, encodable in 3nN3nN3nN bits. The programs read and store those data and compute the observable value; they do not materialize the represented matrix. Ground-state preparation and data generation are excluded from this classical work.

For every fixed subsystem AAA of at most qqq qubits, separately with confidence at least 1−δ1-\delta1−δ,

Ex∥tr⁡Ac(σ^N(x)−ρ(x))∥1≤4qε.\mathbb E_x\left\|\operatorname{tr}_{A^{\mathrm c}} \bigl(\widehat{\sigma}_N(x)-\rho(x)\bigr)\right\|_1 \le\sqrt{4^q\varepsilon}.Ex​​trAc​(σN​(x)−ρ(x))​1​≤4qε​.

Thus taking ε=η2/4q\varepsilon=\eta^2/4^qε=η2/4q gives the informal constant trace-norm error η\etaη on a fixed few-body reduced matrix. This conversion uses the finite Pauli expansion and allocates confidence δ/4q\delta/4^qδ/4q to its coefficients; it leaves the polynomial-in-mmm, linear-in-nnn conclusion intact at fixed accuracy and locality.

This result describes generalization in population average for the source's compact shadow predictor. It asserts neither pointwise error nor simultaneous accuracy on all observables or subsystems, and does not require the predicted representation to be positive or trace one.

Formalization Note Theorem 3 on PDF pp.29–30 explicitly identifies itself as the detailed restatement of Theorem 1. Its Eq. (F3) prints exact ground-state labels, whereas its premise and Eqs. (2), (E3), and (F27) specify shadow labels; the latter determine the model above. This discrepancy and the nonperiodic-boundary gap in Lemma 2 are recorded for independent source moderation, without adding periodicity or a gradient bound as hypotheses.

Target

Theorem 1; detailed Theorem 3, PDF pp.29–30

Fix a finite spatial dimension ddd, bounds on the number and geometric radius of sites in each Hamiltonian term, a local-term density bound bd+cdrdb_d+c_dr^dbd​+cd​rd, a spectral gap γ>0\gamma>0γ>0, an observable locality bound qqq, and a confidence parameter δ∈(0,1)\delta\in(0,1)δ∈(0,1). Consider nnn-qubit Hamiltonians H(x)=∑jhj(x)H(x)=\sum_j h_j(x)H(x)=∑j​hj​(x), smoothly parametrized by x∈[−1,1]mx\in[-1,1]^mx∈[−1,1]m. Each term is Hermitian, obeys ∥hj(x)∥∞≤1\|h_j(x)\|_\infty\le1∥hj​(x)∥∞​≤1, and has directional derivative of operator norm at most one in every Euclidean unit parameter direction. These properties hold throughout the cube; smoothness at its boundary uses a local smooth extension. Every Hamiltonian has an excited energy and a gap at least γ\gammaγ above its entire ground eigenspace. Let ρ(x)\rho(x)ρ(x) be the normalized projector onto that eigenspace, allowing degeneracy.

For a fixed Hermitian observable O=∑i=1LOiO=\sum_{i=1}^L O_iO=∑i=1L​Oi​, each term supported on at most qqq qubits (not necessarily neighboring), choose a norm budget B≥1B\ge1B≥1 satisfying ∑i∥Oi∥∞≤B\sum_i\|O_i\|_\infty\le B∑i​∥Oi​∥∞​≤B. A smaller norm budget may be replaced by one. There are uniform positive constants, depending only on the fixed physical bounds, qqq, and δ\deltaδ, such that for every fixed mean-squared error tolerance ε∈(0,1]\varepsilon\in(0,1]ε∈(0,1] and all sufficiently large mmm, public sample counts, cutoffs, and actual classical arithmetic/RAM programs can be selected before the unknown Hamiltonian family, training draw, observable entries, and test parameter. The training set consists of NNN independent uniform parameter draws, with one fresh-copy randomized Pauli snapshot SℓS_\ellSℓ​ at each point. Pauli axes are independently uniform; the joint measurement outcomes obey the Born law.

The named predictor is

σ^N(x)=1N∑ℓ=1NκΛ(x,xℓ)Sℓ,κΛ(x,y)=∑k∈Zm∥k∥2≤Λcos⁡ ⁣(πk⋅(x−y)).\widehat{\sigma}_N(x)=\frac1N\sum_{\ell=1}^N\kappa_\Lambda(x,x_\ell)S_\ell,\qquad \kappa_\Lambda(x,y)=\sum_{\substack{k\in\mathbb Z^m\\\|k\|_2\le\Lambda}} \cos\!\bigl(\pi k\cdot(x-y)\bigr).σN​(x)=N1​ℓ=1∑N​κΛ​(x,xℓ​)Sℓ​,κΛ​(x,y)=k∈Zm∥k∥2​≤Λ​∑​cos(πk⋅(x−y)).

For each observable fixed before the training draw,

Pr⁡T ⁣[Ex∼Unif[−1,1]m∣tr⁡ ⁣(Oσ^N(x))−tr⁡ ⁣(Oρ(x))∣2≤ε]≥1−δ,\Pr_{\mathcal T}\!\left[ \mathbb E_{x\sim\mathrm{Unif}[-1,1]^m} \left|\operatorname{tr}\!\left(O\widehat{\sigma}_N(x)\right) -\operatorname{tr}\!\left(O\rho(x)\right)\right|^2 \le\varepsilon\right]\ge1-\delta,TPr​[Ex∼Unif[−1,1]m​∣tr(OσN​(x))−tr(Oρ(x))∣2≤ε]≥1−δ,

with N≤CB2mCB2/εN\le C B^2m^{C B^2/\varepsilon}N≤CB2mCB2/ε and computed classical training and prediction work O((n+L)B2mO(B2/ε))O((n+L)B^2m^{O(B^2/\varepsilon)})O((n+L)B2mO(B2/ε)). The compact representation stores mNmNmN real parameter words and nNnNnN six-valued labels, encodable in 3nN3nN3nN bits. The programs read and store those data and compute the observable value; they do not materialize the represented matrix. Ground-state preparation and data generation are excluded from this classical work.

For every fixed subsystem AAA of at most qqq qubits, separately with confidence at least 1−δ1-\delta1−δ,

Ex∥tr⁡Ac(σ^N(x)−ρ(x))∥1≤4qε.\mathbb E_x\left\|\operatorname{tr}_{A^{\mathrm c}} \bigl(\widehat{\sigma}_N(x)-\rho(x)\bigr)\right\|_1 \le\sqrt{4^q\varepsilon}.Ex​​trAc​(σN​(x)−ρ(x))​1​≤4qε​.

Thus taking ε=η2/4q\varepsilon=\eta^2/4^qε=η2/4q gives the informal constant trace-norm error η\etaη on a fixed few-body reduced matrix. This conversion uses the finite Pauli expansion and allocates confidence δ/4q\delta/4^qδ/4q to its coefficients; it leaves the polynomial-in-mmm, linear-in-nnn conclusion intact at fixed accuracy and locality.

This result describes generalization in population average for the source's compact shadow predictor. It asserts neither pointwise error nor simultaneous accuracy on all observables or subsystems, and does not require the predicted representation to be positive or trace one.

Formalization Note Theorem 3 on PDF pp.29–30 explicitly identifies itself as the detailed restatement of Theorem 1. Its Eq. (F3) prints exact ground-state labels, whereas its premise and Eqs. (2), (E3), and (F27) specify shadow labels; the latter determine the model above. This discrepancy and the nonperiodic-boundary gap in Lemma 2 are recorded for independent source moderation, without adding periodicity or a gradient bound as hypotheses.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Provably efficient machine learning for quantum many-body problems, arXiv:2106.12627v4. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Machine LearningQuantum Information·Captain: Goku

Foundations for learning from noisy quantum experimentsResearch Paper

Motivation

Foundations for learning from noisy quantum experiments establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Fix a positive finite dimension ddd and finite labelled sets X,Y,Z,BX,Y,Z,BX,Y,Z,B of preparation actions, dynamics actions, measurement actions, and measurement outcomes. Let Q\mathcal QQ be any set of world models W=({ρx}x∈X,{Ey}y∈Y,{Mzb}z∈Z,b∈B)W=(\{\rho_x\}_{x\in X},\{\mathcal E_y\}_{y\in Y},\{M_{zb}\}_{z\in Z,b\in B})W=({ρx​}x∈X​,{Ey​}y∈Y​,{Mzb​}z∈Z,b∈B​) on Cd\mathbb C^dCd: every preparation is a density matrix, every dynamics action is a CPTP map, and each measurement is a POVM. The model class may be uncountable and may contain equivalent descriptions.

Suppose every W∈QW\in\mathcal QW∈Q is universal: some preparation is pure; some finite collection of dynamics actions implements exact unitary channels whose representatives generate a dense subgroup of SU(d)\mathrm{SU}(d)SU(d); and some measurement effect is not proportional to the identity. These witnessing actions and their physical descriptions are unknown and may vary between worlds. Mathematical inverses enter the generated subgroup; physical access to inverse actions is not assumed.

Then there exists a fixed family (Lk)k∈N(L_k)_{k\in\mathbb N}(Lk​)k∈N​ of finite classical experimental procedures, chosen before the unknown world. Each procedure adaptively chooses experiments that freshly prepare ρx\rho_xρx​, apply a finite word of the available dynamics actions, and measure one of the available POVMs. Its description output is denoted W^(k)=({ρ^x(k)},{E^y(k)},{M^zb(k)})\widehat W^{(k)}=(\{\widehat\rho_x^{(k)}\},\{\widehat{\mathcal E}_y^{(k)}\},\{\widehat M_{zb}^{(k)}\})W(k)=({ρ​x(k)​},{Ey(k)​},{Mzb(k)​}). For every W∈QW\in\mathcal QW∈Q, every ϵ>0\epsilon>0ϵ>0, and every 0<δ<10<\delta<10<δ<1, there exists k0k_0k0​ such that for all k≥k0k\ge k_0k≥k0​ there is one unitary or anti-unitary gauge G\mathcal GG satisfying

Pr⁡W ⁣[∥ρx−G(ρ^x(k))∥1≤ϵ]≥1−δ(x∈X),Pr⁡W ⁣[∥Ey−G∘E^y(k)∘G−1∥⋄≤ϵ]≥1−δ(y∈Y),Pr⁡W ⁣[∥Mzb−G(M^zb(k))∥1≤ϵ]≥1−δ(z∈Z, b∈B).\begin{aligned} \Pr_W\!\left[\|\rho_x-\mathcal G(\widehat\rho_x^{(k)})\|_1\le\epsilon\right]&\ge1-\delta &&(x\in X),\\ \Pr_W\!\left[\|\mathcal E_y-\mathcal G\circ\widehat{\mathcal E}_y^{(k)}\circ\mathcal G^{-1}\|_\diamond\le\epsilon\right]&\ge1-\delta &&(y\in Y),\\ \Pr_W\!\left[\|M_{zb}-\mathcal G(\widehat M_{zb}^{(k)})\|_1\le\epsilon\right]&\ge1-\delta &&(z\in Z,\ b\in B). \end{aligned}WPr​[∥ρx​−G(ρ​x(k)​)∥1​≤ϵ]WPr​[∥Ey​−G∘Ey(k)​∘G−1∥⋄​≤ϵ]WPr​[∥Mzb​−G(Mzb(k)​)∥1​≤ϵ]​≥1−δ≥1−δ≥1−δ​​(x∈X),(y∈Y),(z∈Z, b∈B).​

Here Pr⁡W\Pr_WPrW​ is computed from the experimental outcome probabilities and internal classical randomization of LkL_kLk​. A unitary gauge has the form G(A)=UAU†\mathcal G(A)=UAU^\daggerG(A)=UAU†; an anti-unitary gauge has the form G(A)=UA‾U†\mathcal G(A)=U\overline A U^\daggerG(A)=UAU†. The same gauge is fixed outside all three collections of probability clauses. Both norms are unhalved. The output estimates need not themselves be lawful quantum objects.

The result establishes learnability of all labelled operations from untrusted experiments under universality. It gives eventual accuracy for each world, with no uniform sample bound, polynomial complexity guarantee, or certified accuracy-based stopping rule.

Formalization Note The finite-action scope is explicit in Theorem D.1 (PDF p.21), although the main-text Theorem 2 does not explicitly restrict the action sets. The stage-indexed interpretation follows the precision-halving procedure in D.2 (p.23) and D.7 (p.33).

Target

Theorem 2; formal restatement Theorem D.1 (PDF p.21)

Fix a positive finite dimension ddd and finite labelled sets X,Y,Z,BX,Y,Z,BX,Y,Z,B of preparation actions, dynamics actions, measurement actions, and measurement outcomes. Let Q\mathcal QQ be any set of world models W=({ρx}x∈X,{Ey}y∈Y,{Mzb}z∈Z,b∈B)W=(\{\rho_x\}_{x\in X},\{\mathcal E_y\}_{y\in Y},\{M_{zb}\}_{z\in Z,b\in B})W=({ρx​}x∈X​,{Ey​}y∈Y​,{Mzb​}z∈Z,b∈B​) on Cd\mathbb C^dCd: every preparation is a density matrix, every dynamics action is a CPTP map, and each measurement is a POVM. The model class may be uncountable and may contain equivalent descriptions.

Suppose every W∈QW\in\mathcal QW∈Q is universal: some preparation is pure; some finite collection of dynamics actions implements exact unitary channels whose representatives generate a dense subgroup of SU(d)\mathrm{SU}(d)SU(d); and some measurement effect is not proportional to the identity. These witnessing actions and their physical descriptions are unknown and may vary between worlds. Mathematical inverses enter the generated subgroup; physical access to inverse actions is not assumed.

Then there exists a fixed family (Lk)k∈N(L_k)_{k\in\mathbb N}(Lk​)k∈N​ of finite classical experimental procedures, chosen before the unknown world. Each procedure adaptively chooses experiments that freshly prepare ρx\rho_xρx​, apply a finite word of the available dynamics actions, and measure one of the available POVMs. Its description output is denoted W^(k)=({ρ^x(k)},{E^y(k)},{M^zb(k)})\widehat W^{(k)}=(\{\widehat\rho_x^{(k)}\},\{\widehat{\mathcal E}_y^{(k)}\},\{\widehat M_{zb}^{(k)}\})W(k)=({ρ​x(k)​},{Ey(k)​},{Mzb(k)​}). For every W∈QW\in\mathcal QW∈Q, every ϵ>0\epsilon>0ϵ>0, and every 0<δ<10<\delta<10<δ<1, there exists k0k_0k0​ such that for all k≥k0k\ge k_0k≥k0​ there is one unitary or anti-unitary gauge G\mathcal GG satisfying

Pr⁡W ⁣[∥ρx−G(ρ^x(k))∥1≤ϵ]≥1−δ(x∈X),Pr⁡W ⁣[∥Ey−G∘E^y(k)∘G−1∥⋄≤ϵ]≥1−δ(y∈Y),Pr⁡W ⁣[∥Mzb−G(M^zb(k))∥1≤ϵ]≥1−δ(z∈Z, b∈B).\begin{aligned} \Pr_W\!\left[\|\rho_x-\mathcal G(\widehat\rho_x^{(k)})\|_1\le\epsilon\right]&\ge1-\delta &&(x\in X),\\ \Pr_W\!\left[\|\mathcal E_y-\mathcal G\circ\widehat{\mathcal E}_y^{(k)}\circ\mathcal G^{-1}\|_\diamond\le\epsilon\right]&\ge1-\delta &&(y\in Y),\\ \Pr_W\!\left[\|M_{zb}-\mathcal G(\widehat M_{zb}^{(k)})\|_1\le\epsilon\right]&\ge1-\delta &&(z\in Z,\ b\in B). \end{aligned}WPr​[∥ρx​−G(ρ​x(k)​)∥1​≤ϵ]WPr​[∥Ey​−G∘Ey(k)​∘G−1∥⋄​≤ϵ]WPr​[∥Mzb​−G(Mzb(k)​)∥1​≤ϵ]​≥1−δ≥1−δ≥1−δ​​(x∈X),(y∈Y),(z∈Z, b∈B).​

Here Pr⁡W\Pr_WPrW​ is computed from the experimental outcome probabilities and internal classical randomization of LkL_kLk​. A unitary gauge has the form G(A)=UAU†\mathcal G(A)=UAU^\daggerG(A)=UAU†; an anti-unitary gauge has the form G(A)=UA‾U†\mathcal G(A)=U\overline A U^\daggerG(A)=UAU†. The same gauge is fixed outside all three collections of probability clauses. Both norms are unhalved. The output estimates need not themselves be lawful quantum objects.

The result establishes learnability of all labelled operations from untrusted experiments under universality. It gives eventual accuracy for each world, with no uniform sample bound, polynomial complexity guarantee, or certified accuracy-based stopping rule.

Formalization Note The finite-action scope is explicit in Theorem D.1 (PDF p.21), although the main-text Theorem 2 does not explicitly restrict the action sets. The stage-indexed interpretation follows the precision-halving procedure in D.2 (p.23) and D.7 (p.33).

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Foundations for learning from noisy quantum experiments, arXiv:2204.13691v1. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Machine LearningQuantum Information·Captain: Goku

Robust shadow estimationResearch Paper

Motivation

Robust shadow estimation establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Consider Protocol 1 of Chen, Yu, Zeng and Flammia on n≥1n\ge 1n≥1 qubits, with Hilbert space dimension d=2nd=2^nd=2n. The same completely positive, trace-preserving noise channel Λ\LambdaΛ acts after each ideal global Clifford gate; fixed computational-basis measurement noise is absorbed into Λ\LambdaΛ. Calibration perfectly prepares ∣0⟩⊗n|0\rangle^{\otimes n}∣0⟩⊗n. The full Clifford group modulo global phase is sampled uniformly and calibration shots are independent and identically distributed.

Let ε>0\varepsilon>0ε>0 and 0<δ≤10<\delta\le 10<δ≤1. Define the Z-basis average fidelity by FZ(Λ)=d−1∑b⟨b∣Λ(∣b⟩⟨b∣)∣b⟩F_Z(\Lambda)=d^{-1}\sum_b\langle b|\Lambda(|b\rangle\langle b|)|b\rangleFZ​(Λ)=d−1∑b​⟨b∣Λ(∣b⟩⟨b∣)∣b⟩, and suppose FZ(Λ)>1/dF_Z(\Lambda)>1/dFZ​(Λ)>1/d. Set

A=(1+ε2)(1+1/d)2ε2(FZ(Λ)−1/d)2.A=\frac{(1+\varepsilon^2)(1+1/d)^2}{\varepsilon^2(F_Z(\Lambda)-1/d)^2}.A=ε2(FZ​(Λ)−1/d)2(1+ε2)(1+1/d)2​.

The printed sample scale in Theorem 7 is Rprinted=136ln⁡(2/δ)AR_{\rm printed}=136\ln(2/\delta)ARprinted​=136ln(2/δ)A. Interpret its real-valued batch parameters operationally as positive integers N≥⌈68A⌉N\ge\lceil68A\rceilN≥⌈68A⌉ and K≥⌈2ln⁡(2/δ)⌉K\ge\lceil2\ln(2/\delta)\rceilK≥⌈2ln(2/δ)⌉, with actual calibration count R=NKR=NKR=NK.

For each recorded ideal Clifford UUU and noisy outcome bbb, compute f^(r)=(d∣⟨b∣U(∣0⟩⊗n)∣2−1)/(d−1)\widehat f^{(r)}=(d|\langle b|U(|0\rangle^{\otimes n})|^2-1)/(d-1)f​(r)=(d∣⟨b∣U(∣0⟩⊗n)∣2−1)/(d−1). Let f^\widehat ff​ be the median of the KKK means of batches of NNN such scores. The estimated inverse sends an operator XXX to (Tr⁡X/d)I+f^−1(X−(Tr⁡X/d)I)(\operatorname{Tr}X/d)I+\widehat f^{-1}(X-(\operatorname{Tr}X/d)I)(TrX/d)I+f​−1(X−(TrX/d)I). Let M~(X)=EU[U†MZ(Λ(UXU†))U]\widetilde{\mathcal M}(X)=\mathbb E_U[U^\dagger\mathcal M_Z(\Lambda(UXU^\dagger))U]M(X)=EU​[U†MZ​(Λ(UXU†))U], where MZ\mathcal M_ZMZ​ removes off-diagonal computational-basis entries, and let O0=O−(Tr⁡O/d)IO_0=O-(\operatorname{Tr}O/d)IO0​=O−(TrO/d)I.

With probability at least 1−δ1-\delta1−δ over calibration records, f^≠0\widehat f\ne0f​=0 and the subsequent single-shot retrieval expectation satisfies, simultaneously for every Hermitian observable OOO and every density matrix ρ\rhoρ,

∣EU,b∣ρ[Tr⁡(OM^−1(U†∣b⟩⟨b∣U))]−Tr⁡(Oρ)∣=∣Tr⁡(OM^−1M~(ρ))−Tr⁡(Oρ)∣≤ε∥O0∥∞.\left|\mathbb E_{U,b\mid\rho}[\operatorname{Tr}(O\widehat{\mathcal M}^{-1}(U^\dagger|b\rangle\langle b|U))]-\operatorname{Tr}(O\rho)\right| =\left|\operatorname{Tr}(O\widehat{\mathcal M}^{-1}\widetilde{\mathcal M}(\rho))-\operatorname{Tr}(O\rho)\right| \le\varepsilon\|O_0\|_\infty.​EU,b∣ρ​[Tr(OM−1(U†∣b⟩⟨b∣U))]−Tr(Oρ)​=​Tr(OM−1M(ρ))−Tr(Oρ)​≤ε∥O0​∥∞​.

Here ∥⋅∥∞\|\cdot\|_\infty∥⋅∥∞​ is the operator norm, and the expectation is conditional on the calibration result. This guarantee controls the systematic, asymptotic bias of robust shadow retrieval; it applies to all observables and states on the same successful calibration event.

Formalization Note The statement retains the printed 1+ε21+\varepsilon^21+ε2 factor. The source proof's substitution instead gives (1+ε)2(1+\varepsilon)^2(1+ε)2 from the stated variance bound; this discrepancy and the integer rounding interpretation remain subject to independent source moderation. The product of rounded batch parameters is not asserted to equal, or be bounded above by the ceiling of, the printed total scale. The frozen calibration probability law, overlap scores, median and retrieval expectation compute the named protocol directly.

Target

Theorem 7, Eqs. (B24)-(B25), Protocol 1

Consider Protocol 1 of Chen, Yu, Zeng and Flammia on n≥1n\ge 1n≥1 qubits, with Hilbert space dimension d=2nd=2^nd=2n. The same completely positive, trace-preserving noise channel Λ\LambdaΛ acts after each ideal global Clifford gate; fixed computational-basis measurement noise is absorbed into Λ\LambdaΛ. Calibration perfectly prepares ∣0⟩⊗n|0\rangle^{\otimes n}∣0⟩⊗n. The full Clifford group modulo global phase is sampled uniformly and calibration shots are independent and identically distributed.

Let ε>0\varepsilon>0ε>0 and 0<δ≤10<\delta\le 10<δ≤1. Define the Z-basis average fidelity by FZ(Λ)=d−1∑b⟨b∣Λ(∣b⟩⟨b∣)∣b⟩F_Z(\Lambda)=d^{-1}\sum_b\langle b|\Lambda(|b\rangle\langle b|)|b\rangleFZ​(Λ)=d−1∑b​⟨b∣Λ(∣b⟩⟨b∣)∣b⟩, and suppose FZ(Λ)>1/dF_Z(\Lambda)>1/dFZ​(Λ)>1/d. Set

A=(1+ε2)(1+1/d)2ε2(FZ(Λ)−1/d)2.A=\frac{(1+\varepsilon^2)(1+1/d)^2}{\varepsilon^2(F_Z(\Lambda)-1/d)^2}.A=ε2(FZ​(Λ)−1/d)2(1+ε2)(1+1/d)2​.

The printed sample scale in Theorem 7 is Rprinted=136ln⁡(2/δ)AR_{\rm printed}=136\ln(2/\delta)ARprinted​=136ln(2/δ)A. Interpret its real-valued batch parameters operationally as positive integers N≥⌈68A⌉N\ge\lceil68A\rceilN≥⌈68A⌉ and K≥⌈2ln⁡(2/δ)⌉K\ge\lceil2\ln(2/\delta)\rceilK≥⌈2ln(2/δ)⌉, with actual calibration count R=NKR=NKR=NK.

For each recorded ideal Clifford UUU and noisy outcome bbb, compute f^(r)=(d∣⟨b∣U(∣0⟩⊗n)∣2−1)/(d−1)\widehat f^{(r)}=(d|\langle b|U(|0\rangle^{\otimes n})|^2-1)/(d-1)f​(r)=(d∣⟨b∣U(∣0⟩⊗n)∣2−1)/(d−1). Let f^\widehat ff​ be the median of the KKK means of batches of NNN such scores. The estimated inverse sends an operator XXX to (Tr⁡X/d)I+f^−1(X−(Tr⁡X/d)I)(\operatorname{Tr}X/d)I+\widehat f^{-1}(X-(\operatorname{Tr}X/d)I)(TrX/d)I+f​−1(X−(TrX/d)I). Let M~(X)=EU[U†MZ(Λ(UXU†))U]\widetilde{\mathcal M}(X)=\mathbb E_U[U^\dagger\mathcal M_Z(\Lambda(UXU^\dagger))U]M(X)=EU​[U†MZ​(Λ(UXU†))U], where MZ\mathcal M_ZMZ​ removes off-diagonal computational-basis entries, and let O0=O−(Tr⁡O/d)IO_0=O-(\operatorname{Tr}O/d)IO0​=O−(TrO/d)I.

With probability at least 1−δ1-\delta1−δ over calibration records, f^≠0\widehat f\ne0f​=0 and the subsequent single-shot retrieval expectation satisfies, simultaneously for every Hermitian observable OOO and every density matrix ρ\rhoρ,

∣EU,b∣ρ[Tr⁡(OM^−1(U†∣b⟩⟨b∣U))]−Tr⁡(Oρ)∣=∣Tr⁡(OM^−1M~(ρ))−Tr⁡(Oρ)∣≤ε∥O0∥∞.\left|\mathbb E_{U,b\mid\rho}[\operatorname{Tr}(O\widehat{\mathcal M}^{-1}(U^\dagger|b\rangle\langle b|U))]-\operatorname{Tr}(O\rho)\right| =\left|\operatorname{Tr}(O\widehat{\mathcal M}^{-1}\widetilde{\mathcal M}(\rho))-\operatorname{Tr}(O\rho)\right| \le\varepsilon\|O_0\|_\infty.​EU,b∣ρ​[Tr(OM−1(U†∣b⟩⟨b∣U))]−Tr(Oρ)​=​Tr(OM−1M(ρ))−Tr(Oρ)​≤ε∥O0​∥∞​.

Here ∥⋅∥∞\|\cdot\|_\infty∥⋅∥∞​ is the operator norm, and the expectation is conditional on the calibration result. This guarantee controls the systematic, asymptotic bias of robust shadow retrieval; it applies to all observables and states on the same successful calibration event.

Formalization Note The statement retains the printed 1+ε21+\varepsilon^21+ε2 factor. The source proof's substitution instead gives (1+ε)2(1+\varepsilon)^2(1+ε)2 from the stated variance bound; this discrepancy and the integer rounding interpretation remain subject to independent source moderation. The product of rounded batch parameters is not asserted to equal, or be bounded above by the ceiling of, the printed total scale. The frozen calibration probability law, overlap scores, median and retrieval expectation compute the named protocol directly.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Robust shadow estimation, arXiv:2011.09636v2. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Information·Captain: Goku

A Grand Unification of Quantum AlgorithmsResearch Paper

Motivation

A Grand Unification of Quantum Algorithms establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Fix a nonnegative integer lll, put d=2l+1d=2l+1d=2l+1, and choose real phases ϕ0,…,ϕd−1\phi_0,\ldots,\phi_{d-1}ϕ0​,…,ϕd−1​. There are complex polynomials P,QP,QP,Q, depending only on these phases and lll, with deg⁡P≤d\deg P\le ddegP≤d, deg⁡Q≤d−1\deg Q\le d-1degQ≤d−1, and respective parities ddd and d−1d-1d−1 modulo 222, such that

∣P(x)∣2+(1−x2)∣Q(x)∣2=1for every x∈[−1,1].|P(x)|^2+(1-x^2)|Q(x)|^2=1 \qquad\text{for every }x\in[-1,1].∣P(x)∣2+(1−x2)∣Q(x)∣2=1for every x∈[−1,1].

For every finite quantum register, every pair of normalized pure states ∣A0⟩,∣B0⟩|A_0\rangle,|B_0\rangle∣A0​⟩,∣B0​⟩ in that register, and every unitary UUU with a real nonzero amplitude a=⟨A0∣U∣B0⟩a=\langle A_0|U|B_0\ranglea=⟨A0​∣U∣B0​⟩, define the available exact rank-one phase shifts Aϕ=eiϕ∣A0⟩⟨A0∣A_\phi=e^{i\phi|A_0\rangle\langle A_0|}Aϕ​=eiϕ∣A0​⟩⟨A0​∣ and Bϕ=eiϕ∣B0⟩⟨B0∣B_\phi=e^{i\phi|B_0\rangle\langle B_0|}Bϕ​=eiϕ∣B0​⟩⟨B0​∣ for real ϕ\phiϕ. Then

⟨A0∣Aϕ0[∏k=1lUBϕ2k−1U†Aϕ2k]U∣B0⟩=P(a).\langle A_0|A_{\phi_0}\left[\prod_{k=1}^{l}U B_{\phi_{2k-1}}U^\dagger A_{\phi_{2k}}\right]U|B_0\rangle=P(a).⟨A0​∣Aϕ0​​[k=1∏l​UBϕ2k−1​​U†Aϕ2k​​]U∣B0​⟩=P(a).

The product is written in increasing kkk from left to right, and its rightmost UUU acts first. Normalization and unitarity imply a∈[−1,1]a\in[-1,1]a∈[−1,1]; the endpoints a=±1a=\pm1a=±1 are allowed. Parity means P(−x)=(−1)dP(x)P(-x)=(-1)^dP(x)P(−x)=(−1)dP(x) and Q(−x)=(−1)d−1Q(x)Q(-x)=(-1)^{d-1}Q(x)Q(−x)=(−1)d−1Q(x).

This construction applies one uniform polynomial to a privileged transition amplitude and connects amplitude amplification with quantum signal processing.

Formalization Note The finite register is a Euclidean space over an arbitrary finite basis type. The frozen positive-sign rank-one phase shifts and sequence encode Eq. (13) exactly. The complementary polynomial is existentially quantified with PPP before the register, states, unitary and amplitude. The zero polynomial is allowed as QQQ, including when l=0l=0l=0.

Target

Theorem 2 (Amplitude Amplification), Section II B, Eq. (13)

Fix a nonnegative integer lll, put d=2l+1d=2l+1d=2l+1, and choose real phases ϕ0,…,ϕd−1\phi_0,\ldots,\phi_{d-1}ϕ0​,…,ϕd−1​. There are complex polynomials P,QP,QP,Q, depending only on these phases and lll, with deg⁡P≤d\deg P\le ddegP≤d, deg⁡Q≤d−1\deg Q\le d-1degQ≤d−1, and respective parities ddd and d−1d-1d−1 modulo 222, such that

∣P(x)∣2+(1−x2)∣Q(x)∣2=1for every x∈[−1,1].|P(x)|^2+(1-x^2)|Q(x)|^2=1 \qquad\text{for every }x\in[-1,1].∣P(x)∣2+(1−x2)∣Q(x)∣2=1for every x∈[−1,1].

For every finite quantum register, every pair of normalized pure states ∣A0⟩,∣B0⟩|A_0\rangle,|B_0\rangle∣A0​⟩,∣B0​⟩ in that register, and every unitary UUU with a real nonzero amplitude a=⟨A0∣U∣B0⟩a=\langle A_0|U|B_0\ranglea=⟨A0​∣U∣B0​⟩, define the available exact rank-one phase shifts Aϕ=eiϕ∣A0⟩⟨A0∣A_\phi=e^{i\phi|A_0\rangle\langle A_0|}Aϕ​=eiϕ∣A0​⟩⟨A0​∣ and Bϕ=eiϕ∣B0⟩⟨B0∣B_\phi=e^{i\phi|B_0\rangle\langle B_0|}Bϕ​=eiϕ∣B0​⟩⟨B0​∣ for real ϕ\phiϕ. Then

⟨A0∣Aϕ0[∏k=1lUBϕ2k−1U†Aϕ2k]U∣B0⟩=P(a).\langle A_0|A_{\phi_0}\left[\prod_{k=1}^{l}U B_{\phi_{2k-1}}U^\dagger A_{\phi_{2k}}\right]U|B_0\rangle=P(a).⟨A0​∣Aϕ0​​[k=1∏l​UBϕ2k−1​​U†Aϕ2k​​]U∣B0​⟩=P(a).

The product is written in increasing kkk from left to right, and its rightmost UUU acts first. Normalization and unitarity imply a∈[−1,1]a\in[-1,1]a∈[−1,1]; the endpoints a=±1a=\pm1a=±1 are allowed. Parity means P(−x)=(−1)dP(x)P(-x)=(-1)^dP(x)P(−x)=(−1)dP(x) and Q(−x)=(−1)d−1Q(x)Q(-x)=(-1)^{d-1}Q(x)Q(−x)=(−1)d−1Q(x).

This construction applies one uniform polynomial to a privileged transition amplitude and connects amplitude amplification with quantum signal processing.

Formalization Note The finite register is a Euclidean space over an arbitrary finite basis type. The frozen positive-sign rank-one phase shifts and sequence encode Eq. (13) exactly. The complementary polynomial is existentially quantified with PPP before the register, states, unitary and amplitude. The zero polynomial is allowed as QQQ, including when l=0l=0l=0.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • A Grand Unification of Quantum Algorithms, arXiv:2105.02859v5. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Error CorrectionQuantum Information·Captain: Goku

Quantum Expander CodesResearch Paper

Motivation

Quantum Expander Codes establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Fix positive integer degrees ΔA,ΔB\Delta_A,\Delta_BΔA​,ΔB​ and positive real constants γA,δA,γB,δB\gamma_A,\delta_A,\gamma_B,\delta_BγA​,δA​,γB​,δB​, with δA,δB<1/6\delta_A,\delta_B<1/6δA​,δB​<1/6. There are a deterministic classical decoder, a constant C>0C>0C>0, and an integer n0n_0n0​, all chosen before the graph sizes and inputs, with the following properties.

Let G=(A⊔B,E)G=(A\sqcup B,E)G=(A⊔B,E) be any finite simple bipartite graph with 1≤nB=∣B∣≤nA=∣A∣1\le n_B=|B|\le n_A=|A|1≤nB​=∣B∣≤nA​=∣A∣, left degree ΔA\Delta_AΔA​ and right degree ΔB\Delta_BΔB​. For every S⊆AS\subseteq AS⊆A with ∣S∣≤γAnA|S|\le\gamma_A n_A∣S∣≤γA​nA​, require ∣Γ(S)∣≥(1−δA)ΔA∣S∣|\Gamma(S)|\ge(1-\delta_A)\Delta_A|S|∣Γ(S)∣≥(1−δA​)ΔA​∣S∣, where Γ(S)\Gamma(S)Γ(S) denotes its neighboring vertices. Require the corresponding right expansion for every S⊆BS\subseteq BS⊆B with ∣S∣≤γBnB|S|\le\gamma_B n_B∣S∣≤γB​nB​.

Form the self hypergraph-product CSS code on the tagged coordinates Q=(A×A)⊔(B×B)Q=(A\times A)\sqcup(B\times B)Q=(A×A)⊔(B×B), of length n=nA2+nB2n=n_A^2+n_B^2n=nA2​+nB2​. Write HHH for the binary incidence matrix with rows BBB and columns AAA, and set HX=[IA⊗H∣HT⊗IB]H_X=[I_A\otimes H\mid H^{\mathsf T}\otimes I_B]HX​=[IA​⊗H∣HT⊗IB​], HZ=[H⊗IA∣IB⊗HT]H_Z=[H\otimes I_A\mid I_B\otimes H^{\mathsf T}]HZ​=[H⊗IA​∣IB​⊗HT]. Let RXR_XRX​ and RZR_ZRZ​ be their respective binary row spaces.

On every syndrome input, the decoder terminates and realizes the Section 3 small-set-flip algorithm, treating the two components independently. Each step flips a nonempty subset of an opposite generator's support, strictly reduces syndrome weight, and maximizes the decrease divided by the number of flipped coordinates. The deterministic implementation fixes its choices among the finitely many tied candidates. A zero syndrome returns the accumulated correction; a nonzero syndrome with no improving flip returns failure. Whenever n≥n0n\ge n_0n≥n0​, its total uniform-cost word-machine instruction count, together with the cost of loading its adjacency-list and syndrome input, is at most CnCnCn.

For every binary error pair e=(eX,eZ)e=(e_X,e_Z)e=(eX​,eZ​) on QQQ, let w(e)w(e)w(e) count coordinates on which at least one component is nonzero. If

w(e)<w0:=min⁡(γAnA,γBnB)3(1+ΔB),w(e)<w_0:=\frac{\min(\gamma_A n_A,\gamma_B n_B)}{3(1+\Delta_B)},w(e)<w0​:=3(1+ΔB​)min(γA​nA​,γB​nB​)​,

then on the exact syndrome (HXeX,HZeZ)(H_Xe_X,H_Ze_Z)(HX​eX​,HZ​eZ​) the decoder returns a correction (cX,cZ)(c_X,c_Z)(cX​,cZ​) satisfying

cX+eX∈RZ,cZ+eZ∈RX.c_X+e_X\in R_Z,\qquad c_Z+e_Z\in R_X.cX​+eX​∈RZ​,cZ​+eZ​∈RX​.

Correctness holds at every admissible finite size. This is an exact adversarial decoding guarantee for the associated quantum code, with linear classical runtime when degrees are fixed.

Formalization Note The positive-degree, nonempty-part convention used in the paper's proof is explicit. Equation (6)'s mixed coordinate names are read as the supports of the HXH_XHX​ rows fixed by Equation (1) and the incidence formulas. These source clarifications are disclosed for independent moderation; the strict threshold and all constants in it are unchanged. Runtime and realization are conclusions about an executable classical machine; no progress or minimum-distance assertion is a hypothesis.

Target

Theorem 2

Fix positive integer degrees ΔA,ΔB\Delta_A,\Delta_BΔA​,ΔB​ and positive real constants γA,δA,γB,δB\gamma_A,\delta_A,\gamma_B,\delta_BγA​,δA​,γB​,δB​, with δA,δB<1/6\delta_A,\delta_B<1/6δA​,δB​<1/6. There are a deterministic classical decoder, a constant C>0C>0C>0, and an integer n0n_0n0​, all chosen before the graph sizes and inputs, with the following properties.

Let G=(A⊔B,E)G=(A\sqcup B,E)G=(A⊔B,E) be any finite simple bipartite graph with 1≤nB=∣B∣≤nA=∣A∣1\le n_B=|B|\le n_A=|A|1≤nB​=∣B∣≤nA​=∣A∣, left degree ΔA\Delta_AΔA​ and right degree ΔB\Delta_BΔB​. For every S⊆AS\subseteq AS⊆A with ∣S∣≤γAnA|S|\le\gamma_A n_A∣S∣≤γA​nA​, require ∣Γ(S)∣≥(1−δA)ΔA∣S∣|\Gamma(S)|\ge(1-\delta_A)\Delta_A|S|∣Γ(S)∣≥(1−δA​)ΔA​∣S∣, where Γ(S)\Gamma(S)Γ(S) denotes its neighboring vertices. Require the corresponding right expansion for every S⊆BS\subseteq BS⊆B with ∣S∣≤γBnB|S|\le\gamma_B n_B∣S∣≤γB​nB​.

Form the self hypergraph-product CSS code on the tagged coordinates Q=(A×A)⊔(B×B)Q=(A\times A)\sqcup(B\times B)Q=(A×A)⊔(B×B), of length n=nA2+nB2n=n_A^2+n_B^2n=nA2​+nB2​. Write HHH for the binary incidence matrix with rows BBB and columns AAA, and set HX=[IA⊗H∣HT⊗IB]H_X=[I_A\otimes H\mid H^{\mathsf T}\otimes I_B]HX​=[IA​⊗H∣HT⊗IB​], HZ=[H⊗IA∣IB⊗HT]H_Z=[H\otimes I_A\mid I_B\otimes H^{\mathsf T}]HZ​=[H⊗IA​∣IB​⊗HT]. Let RXR_XRX​ and RZR_ZRZ​ be their respective binary row spaces.

On every syndrome input, the decoder terminates and realizes the Section 3 small-set-flip algorithm, treating the two components independently. Each step flips a nonempty subset of an opposite generator's support, strictly reduces syndrome weight, and maximizes the decrease divided by the number of flipped coordinates. The deterministic implementation fixes its choices among the finitely many tied candidates. A zero syndrome returns the accumulated correction; a nonzero syndrome with no improving flip returns failure. Whenever n≥n0n\ge n_0n≥n0​, its total uniform-cost word-machine instruction count, together with the cost of loading its adjacency-list and syndrome input, is at most CnCnCn.

For every binary error pair e=(eX,eZ)e=(e_X,e_Z)e=(eX​,eZ​) on QQQ, let w(e)w(e)w(e) count coordinates on which at least one component is nonzero. If

w(e)<w0:=min⁡(γAnA,γBnB)3(1+ΔB),w(e)<w_0:=\frac{\min(\gamma_A n_A,\gamma_B n_B)}{3(1+\Delta_B)},w(e)<w0​:=3(1+ΔB​)min(γA​nA​,γB​nB​)​,

then on the exact syndrome (HXeX,HZeZ)(H_Xe_X,H_Ze_Z)(HX​eX​,HZ​eZ​) the decoder returns a correction (cX,cZ)(c_X,c_Z)(cX​,cZ​) satisfying

cX+eX∈RZ,cZ+eZ∈RX.c_X+e_X\in R_Z,\qquad c_Z+e_Z\in R_X.cX​+eX​∈RZ​,cZ​+eZ​∈RX​.

Correctness holds at every admissible finite size. This is an exact adversarial decoding guarantee for the associated quantum code, with linear classical runtime when degrees are fixed.

Formalization Note The positive-degree, nonempty-part convention used in the paper's proof is explicit. Equation (6)'s mixed coordinate names are read as the supports of the HXH_XHX​ rows fixed by Equation (1) and the incidence formulas. These source clarifications are disclosed for independent moderation; the strict threshold and all constants in it are unchanged. Runtime and realization are conclusions about an executable classical machine; no progress or minimum-distance assertion is a hypothesis.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Quantum Expander Codes, arXiv:1504.00822v1. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Information·Captain: Goku

Simulating Hamiltonian dynamics with a truncated Taylor seriesResearch Paper

Motivation

Simulating Hamiltonian dynamics with a truncated Taylor series establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let D,L≥1D,L\ge1D,L≥1, let α1,…,αL>0\alpha_1,\ldots,\alpha_L>0α1​,…,αL​>0 be known coefficients, and let t>0t>0t>0 and 0<ϵ<10<\epsilon<10<ϵ<1. For any unitary matrices H1,…,HLH_1,\ldots,H_LH1​,…,HL​ on a DDD-dimensional system whose sum H=∑ℓ=1LαℓHℓH=\sum_{\ell=1}^L\alpha_\ell H_\ellH=∑ℓ=1L​αℓ​Hℓ​ is Hermitian, count coherent signed controlled selection ∣b,ℓ,ψ⟩↦∣b,ℓ⟩(−iHℓ)b∣ψ⟩|b,\ell,\psi\rangle\mapsto|b,\ell\rangle(-iH_\ell)^b|\psi\rangle∣b,ℓ,ψ⟩↦∣b,ℓ⟩(−iHℓ​)b∣ψ⟩ and its inverse as the access operations. Set T=t∑ℓαℓT=t\sum_\ell\alpha_\ellT=t∑ℓ​αℓ​, r=⌈T/ln⁡2⌉r=\lceil T/\ln2\rceilr=⌈T/ln2⌉, and n=⌈log⁡2D⌉n=\lceil\log_2D\rceiln=⌈log2​D⌉.

There are absolute constants C>0C>0C>0, c≥1c\ge1c≥1, and q0>exp⁡(exp⁡(1))q_0>\exp(\exp(1))q0​>exp(exp(1)), chosen before all instance data, for which the following holds. Choose the least nonnegative truncation order KKK satisfying ∑k=K+1∞(ln⁡2)k/k!≤ϵ/(cr)\sum_{k=K+1}^{\infty}(\ln2)^k/k!\le\epsilon/(cr)∑k=K+1∞​(ln2)k/k!≤ϵ/(cr). From D,L,α,t,ϵD,L,\alpha,t,\epsilonD,L,α,t,ϵ alone one can construct the paper's segmented Taylor simulator, before choosing the term oracle or the input state. The simulator uses r−1r-1r−1 segments of duration ln⁡2/∑ℓαℓ\ln2/\sum_\ell\alpha_\ellln2/∑ℓ​αℓ​ and the remaining positive duration as its final segment. Each segment uses the Taylor LCU, the normalization ancilla, and robust oblivious amplification −WRW†RW-WRW^\dagger RW−WRW†RW, with fresh zero ancillas that are subsequently discarded.

If JJJ is the standard isometric embedding of the DDD-dimensional system into nnn qubits, S\mathcal SS denotes the implemented unconditional channel, and ψ\psiψ is any unit vector, then

∥S(J∣ψ⟩⟨ψ∣J†)−Je−iHt∣ψ⟩⟨ψ∣eiHtJ†∥1≤ϵ.\left\|\mathcal S(J|\psi\rangle\langle\psi|J^\dagger) -J e^{-iHt}|\psi\rangle\langle\psi|e^{iHt}J^\dagger\right\|_1\le\epsilon.​S(J∣ψ⟩⟨ψ∣J†)−Je−iHt∣ψ⟩⟨ψ∣eiHtJ†​1​≤ϵ.

Every segment's truncated operator differs from its exact evolution by at most ϵ/(cr)\epsilon/(cr)ϵ/(cr) in spectral norm. The same construction also approximates the padded Hamiltonian on every normalized state of the full qubit register. The number of signed-selector calls is at most Cr(K+1)Cr(K+1)Cr(K+1); the number of other elementary gates is at most CLr(K+1)CLr(K+1)CLr(K+1); and peak ancillary qubits, treating the selector as the primitive access operation, are at most C(1+⌈log⁡2L⌉)(K+1)C(1+\lceil\log_2L\rceil)(K+1)C(1+⌈log2​L⌉)(K+1).

For T≥1T\ge1T≥1 and T/ϵ≥q0T/\epsilon\ge q_0T/ϵ≥q0​, the order and counted access cost satisfy

K≤Clog⁡(T/ϵ)log⁡log⁡(T/ϵ),Q≤CTlog⁡(T/ϵ)log⁡log⁡(T/ϵ).K\le C\frac{\log(T/\epsilon)}{\log\log(T/\epsilon)},\qquad Q\le CT\frac{\log(T/\epsilon)}{\log\log(T/\epsilon)}.K≤Cloglog(T/ϵ)log(T/ϵ)​,Q≤CTloglog(T/ϵ)log(T/ϵ)​.

If a signed-selector implementation has ggg elementary gates and www clean workspace qubits, there are elementary segment circuits implementing the same simulator, returning that workspace to zero, with total gate count at most C(L+g)r(K+1)C(L+g)r(K+1)C(L+g)r(K+1). In the special case in which the padded terms are tensor products of single-qubit Pauli matrices, such circuits exist with total gate count at most CL(n+1+⌈log⁡2L⌉)r(K+1)CL(n+1+\lceil\log_2L\rceil)r(K+1)CL(n+1+⌈log2​L⌉)r(K+1) and peak ancillary qubits at most C(1+⌈log⁡2L⌉)(K+1)C(1+\lceil\log_2L\rceil)(K+1)C(1+⌈log2​L⌉)(K+1).

This gives the paper's time-independent simulation cost without requiring commuting, self-inverse, Hermitian individual terms or a bound on ∥H∥\|H\|∥H∥.

Formalization Note The paper does not name the reduced-state norm. Trace norm without the factor 1/21/21/2 is used to make its discard-ancillas and error-accumulation argument precise. Eq. (10)'s failure coefficient, Eq. (16)'s partial trace of a ket, and the printed order-register amplitude are corrected as recorded in the audit. Arbitrary one- and two-qubit gates are used, with exact rotations and inverses; finite-gate-set synthesis overhead is outside the claim.

Target

Unnumbered time-independent simulation bound; construction pp.3–4, Eqs. (18)–(24)

Let D,L≥1D,L\ge1D,L≥1, let α1,…,αL>0\alpha_1,\ldots,\alpha_L>0α1​,…,αL​>0 be known coefficients, and let t>0t>0t>0 and 0<ϵ<10<\epsilon<10<ϵ<1. For any unitary matrices H1,…,HLH_1,\ldots,H_LH1​,…,HL​ on a DDD-dimensional system whose sum H=∑ℓ=1LαℓHℓH=\sum_{\ell=1}^L\alpha_\ell H_\ellH=∑ℓ=1L​αℓ​Hℓ​ is Hermitian, count coherent signed controlled selection ∣b,ℓ,ψ⟩↦∣b,ℓ⟩(−iHℓ)b∣ψ⟩|b,\ell,\psi\rangle\mapsto|b,\ell\rangle(-iH_\ell)^b|\psi\rangle∣b,ℓ,ψ⟩↦∣b,ℓ⟩(−iHℓ​)b∣ψ⟩ and its inverse as the access operations. Set T=t∑ℓαℓT=t\sum_\ell\alpha_\ellT=t∑ℓ​αℓ​, r=⌈T/ln⁡2⌉r=\lceil T/\ln2\rceilr=⌈T/ln2⌉, and n=⌈log⁡2D⌉n=\lceil\log_2D\rceiln=⌈log2​D⌉.

There are absolute constants C>0C>0C>0, c≥1c\ge1c≥1, and q0>exp⁡(exp⁡(1))q_0>\exp(\exp(1))q0​>exp(exp(1)), chosen before all instance data, for which the following holds. Choose the least nonnegative truncation order KKK satisfying ∑k=K+1∞(ln⁡2)k/k!≤ϵ/(cr)\sum_{k=K+1}^{\infty}(\ln2)^k/k!\le\epsilon/(cr)∑k=K+1∞​(ln2)k/k!≤ϵ/(cr). From D,L,α,t,ϵD,L,\alpha,t,\epsilonD,L,α,t,ϵ alone one can construct the paper's segmented Taylor simulator, before choosing the term oracle or the input state. The simulator uses r−1r-1r−1 segments of duration ln⁡2/∑ℓαℓ\ln2/\sum_\ell\alpha_\ellln2/∑ℓ​αℓ​ and the remaining positive duration as its final segment. Each segment uses the Taylor LCU, the normalization ancilla, and robust oblivious amplification −WRW†RW-WRW^\dagger RW−WRW†RW, with fresh zero ancillas that are subsequently discarded.

If JJJ is the standard isometric embedding of the DDD-dimensional system into nnn qubits, S\mathcal SS denotes the implemented unconditional channel, and ψ\psiψ is any unit vector, then

∥S(J∣ψ⟩⟨ψ∣J†)−Je−iHt∣ψ⟩⟨ψ∣eiHtJ†∥1≤ϵ.\left\|\mathcal S(J|\psi\rangle\langle\psi|J^\dagger) -J e^{-iHt}|\psi\rangle\langle\psi|e^{iHt}J^\dagger\right\|_1\le\epsilon.​S(J∣ψ⟩⟨ψ∣J†)−Je−iHt∣ψ⟩⟨ψ∣eiHtJ†​1​≤ϵ.

Every segment's truncated operator differs from its exact evolution by at most ϵ/(cr)\epsilon/(cr)ϵ/(cr) in spectral norm. The same construction also approximates the padded Hamiltonian on every normalized state of the full qubit register. The number of signed-selector calls is at most Cr(K+1)Cr(K+1)Cr(K+1); the number of other elementary gates is at most CLr(K+1)CLr(K+1)CLr(K+1); and peak ancillary qubits, treating the selector as the primitive access operation, are at most C(1+⌈log⁡2L⌉)(K+1)C(1+\lceil\log_2L\rceil)(K+1)C(1+⌈log2​L⌉)(K+1).

For T≥1T\ge1T≥1 and T/ϵ≥q0T/\epsilon\ge q_0T/ϵ≥q0​, the order and counted access cost satisfy

K≤Clog⁡(T/ϵ)log⁡log⁡(T/ϵ),Q≤CTlog⁡(T/ϵ)log⁡log⁡(T/ϵ).K\le C\frac{\log(T/\epsilon)}{\log\log(T/\epsilon)},\qquad Q\le CT\frac{\log(T/\epsilon)}{\log\log(T/\epsilon)}.K≤Cloglog(T/ϵ)log(T/ϵ)​,Q≤CTloglog(T/ϵ)log(T/ϵ)​.

If a signed-selector implementation has ggg elementary gates and www clean workspace qubits, there are elementary segment circuits implementing the same simulator, returning that workspace to zero, with total gate count at most C(L+g)r(K+1)C(L+g)r(K+1)C(L+g)r(K+1). In the special case in which the padded terms are tensor products of single-qubit Pauli matrices, such circuits exist with total gate count at most CL(n+1+⌈log⁡2L⌉)r(K+1)CL(n+1+\lceil\log_2L\rceil)r(K+1)CL(n+1+⌈log2​L⌉)r(K+1) and peak ancillary qubits at most C(1+⌈log⁡2L⌉)(K+1)C(1+\lceil\log_2L\rceil)(K+1)C(1+⌈log2​L⌉)(K+1).

This gives the paper's time-independent simulation cost without requiring commuting, self-inverse, Hermitian individual terms or a bound on ∥H∥\|H\|∥H∥.

Formalization Note The paper does not name the reduced-state norm. Trace norm without the factor 1/21/21/2 is used to make its discard-ancillas and error-accumulation argument precise. Eq. (10)'s failure coefficient, Eq. (16)'s partial trace of a ket, and the printed order-register amplitude are corrected as recorded in the audit. Arbitrary one- and two-qubit gates are used, with exact rotations and inverses; finite-gate-set synthesis overhead is outside the claim.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Simulating Hamiltonian dynamics with a truncated Taylor series, arXiv:1412.4687v1. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
Quantum Information·Captain: Goku

Quantum algorithm for systems of linear equations with exponentially improved dependence on precisionResearch Paper

Motivation

Quantum algorithm for systems of linear equations with exponentially improved dependence on precision establishes the selected mathematical guarantees below. The mission turns those original paper results into precise Lean proof targets.

Setting

Let N≥1N\ge1N≥1, let A∈CN×NA\in\mathbb C^{N\times N}A∈CN×N be Hermitian and invertible with ∥A∥op=1\|A\|_{\mathrm{op}}=1∥A∥op​=1, and let κ≥1\kappa\ge1κ≥1 be a supplied upper bound on its condition number. Let b≠0b\ne0b=0, and write ∣b⟩=b/∥b∥|b\rangle=b/\|b\|∣b⟩=b/∥b∥ and ∣x⟩=A−1b/∥A−1b∥|x\rangle=A^{-1}b/\|A^{-1}b\|∣x⟩=A−1b/∥A−1b∥. The coherent preparation procedure PBP_BPB​ prepares ∣b⟩|b\rangle∣b⟩ in polynomial time in log⁡N\log NlogN on the ⌈log⁡2N⌉\lceil\log_2 N\rceil⌈log2​N⌉-qubit state register; its inverse is available. Put L=max⁡{1,log⁡(κ/ε)}L=\max\{1,\log(\kappa/\varepsilon)\}L=max{1,log(κ/ε)}, with 0<ε<10<\varepsilon<10<ε<1.

There are absolute positive constants and fixed asymptotic thresholds, chosen before all public parameters and hidden inputs, with the following two conclusions.

  1. A single oracle-independent Fourier reduction for the public parameters solves the problem for every such A,b,PBA,b,P_BA,b,PB​ and every compatible coherent SELECT simulator. Sparsity is not needed for this conclusion. SELECT implements the signed evolutions used by the Fourier sum, uniformly on superpositions and with reverse access. Its maximum evolution time, required operator error, number of calls, and number of preparation calls satisfy
∣t∣≤CtκL,η=CηεκL,QSELECT,QPB≤CcallsκL.|t|\le C_t\kappa L,\qquad \eta=C_\eta\frac{\varepsilon}{\kappa\sqrt L},\qquad Q_{\mathrm{SELECT}},Q_{P_B}\le C_{\mathrm{calls}}\kappa\sqrt L.∣t∣≤Ct​κL,η=Cη​κL​ε​,QSELECT​,QPB​​≤Ccalls​κL​.

The reduction outputs a success flag with probability at least 1/21/21/2. Conditional on success, its system output is the pure state whose vector representative is the normalized action of the actually simulated Fourier block on ∣b⟩|b\rangle∣b⟩, and

∥∣x~⟩−∣x⟩∥2≤ε.\bigl\||\widetilde x\rangle-|x\rangle\bigr\|_2\le\varepsilon.​∣x⟩−∣x⟩​2​≤ε.

This representative is fixed by the Fourier block; the error is not minimized over global phases. Failure output is unrestricted.

  1. If AAA has at most ddd nonzero entries in each row and column, with 1≤d≤N1\le d\le N1≤d≤N, and PAP_APA​ supplies both the in-place column-location oracle and the XOR entry oracle of equations (1)–(2), then there is a concrete sparse implementation with the same output guarantee and worst-case bounds
QPA≤CAdκ2L5/2,QPB≤CcallsκL,Gexternal≤CGdκ2L5/2(log⁡N+L5/2).Q_{P_A}\le C_A d\kappa^2L^{5/2},\qquad Q_{P_B}\le C_{\mathrm{calls}}\kappa\sqrt L,\qquad G_{\mathrm{external}}\le C_Gd\kappa^2L^{5/2}\bigl(\log N+L^{5/2}\bigr).QPA​​≤CA​dκ2L5/2,QPB​​≤Ccalls​κL​,Gexternal​≤CG​dκ2L5/2(logN+L5/2).

The sum QPAQ_{P_A}QPA​​ counts the two matrix-oracle operations separately and then adds them. Short columns may be padded with zero entries, the location lists need not be sorted, and injectivity of each in-place location map is required. Entries use a public ordinary signed binary complex-number format. This is the exact-entry branch of the paper's access model; sufficiently accurate finite-precision access is covered through the simulator error budget. No controlled access to the input black boxes is assumed. External gates exclude internal implementations of PAP_APA​ and PBP_BPB​; inlining either subroutine adds its per-call gate cost times its corresponding number of calls.

The bounds establish logarithmic dependence on output precision for quantum state preparation. The number of calls is bounded in the worst case using a finite capped amplification routine.

Formalization Note The Lean conclusion includes both clauses in one theorem and fixes the reduction and sparse circuits before quantifying over hidden inputs. The preparation-time polynomial and binary format are public parameters. Successful output is represented by a subnormalized pure density matrix together with its explicitly specified vector representative and direct vector error. Invalid qubit padding cannot count as successful output.

Correction to the printed source.

Printed: Page 8 says a worst-case amplification guarantee needs an 'upper bound on the probability q'; page 15 writes 'τ := y_J y_K'.

Corrected: Use a known positive lower bound on q for capped amplification, as Corollary 10 does, and read the maximum evolution time as y_J z_K.

Reason: The required amplification work grows when q decreases; Corollary 10 provides q bounded below using known coefficient mass. The Fourier times are y_j z_k in (18), (31), (52); y_K is not the defined z cutoff.

Target

Theorem 3 (Fourier approach)

Let N≥1N\ge1N≥1, let A∈CN×NA\in\mathbb C^{N\times N}A∈CN×N be Hermitian and invertible with ∥A∥op=1\|A\|_{\mathrm{op}}=1∥A∥op​=1, and let κ≥1\kappa\ge1κ≥1 be a supplied upper bound on its condition number. Let b≠0b\ne0b=0, and write ∣b⟩=b/∥b∥|b\rangle=b/\|b\|∣b⟩=b/∥b∥ and ∣x⟩=A−1b/∥A−1b∥|x\rangle=A^{-1}b/\|A^{-1}b\|∣x⟩=A−1b/∥A−1b∥. The coherent preparation procedure PBP_BPB​ prepares ∣b⟩|b\rangle∣b⟩ in polynomial time in log⁡N\log NlogN on the ⌈log⁡2N⌉\lceil\log_2 N\rceil⌈log2​N⌉-qubit state register; its inverse is available. Put L=max⁡{1,log⁡(κ/ε)}L=\max\{1,\log(\kappa/\varepsilon)\}L=max{1,log(κ/ε)}, with 0<ε<10<\varepsilon<10<ε<1.

There are absolute positive constants and fixed asymptotic thresholds, chosen before all public parameters and hidden inputs, with the following two conclusions.

  1. A single oracle-independent Fourier reduction for the public parameters solves the problem for every such A,b,PBA,b,P_BA,b,PB​ and every compatible coherent SELECT simulator. Sparsity is not needed for this conclusion. SELECT implements the signed evolutions used by the Fourier sum, uniformly on superpositions and with reverse access. Its maximum evolution time, required operator error, number of calls, and number of preparation calls satisfy
∣t∣≤CtκL,η=CηεκL,QSELECT,QPB≤CcallsκL.|t|\le C_t\kappa L,\qquad \eta=C_\eta\frac{\varepsilon}{\kappa\sqrt L},\qquad Q_{\mathrm{SELECT}},Q_{P_B}\le C_{\mathrm{calls}}\kappa\sqrt L.∣t∣≤Ct​κL,η=Cη​κL​ε​,QSELECT​,QPB​​≤Ccalls​κL​.

The reduction outputs a success flag with probability at least 1/21/21/2. Conditional on success, its system output is the pure state whose vector representative is the normalized action of the actually simulated Fourier block on ∣b⟩|b\rangle∣b⟩, and

∥∣x~⟩−∣x⟩∥2≤ε.\bigl\||\widetilde x\rangle-|x\rangle\bigr\|_2\le\varepsilon.​∣x⟩−∣x⟩​2​≤ε.

This representative is fixed by the Fourier block; the error is not minimized over global phases. Failure output is unrestricted.

  1. If AAA has at most ddd nonzero entries in each row and column, with 1≤d≤N1\le d\le N1≤d≤N, and PAP_APA​ supplies both the in-place column-location oracle and the XOR entry oracle of equations (1)–(2), then there is a concrete sparse implementation with the same output guarantee and worst-case bounds
QPA≤CAdκ2L5/2,QPB≤CcallsκL,Gexternal≤CGdκ2L5/2(log⁡N+L5/2).Q_{P_A}\le C_A d\kappa^2L^{5/2},\qquad Q_{P_B}\le C_{\mathrm{calls}}\kappa\sqrt L,\qquad G_{\mathrm{external}}\le C_Gd\kappa^2L^{5/2}\bigl(\log N+L^{5/2}\bigr).QPA​​≤CA​dκ2L5/2,QPB​​≤Ccalls​κL​,Gexternal​≤CG​dκ2L5/2(logN+L5/2).

The sum QPAQ_{P_A}QPA​​ counts the two matrix-oracle operations separately and then adds them. Short columns may be padded with zero entries, the location lists need not be sorted, and injectivity of each in-place location map is required. Entries use a public ordinary signed binary complex-number format. This is the exact-entry branch of the paper's access model; sufficiently accurate finite-precision access is covered through the simulator error budget. No controlled access to the input black boxes is assumed. External gates exclude internal implementations of PAP_APA​ and PBP_BPB​; inlining either subroutine adds its per-call gate cost times its corresponding number of calls.

The bounds establish logarithmic dependence on output precision for quantum state preparation. The number of calls is bounded in the worst case using a finite capped amplification routine.

Formalization Note The Lean conclusion includes both clauses in one theorem and fixes the reduction and sparse circuits before quantifying over hidden inputs. The preparation-time polynomial and binary format are public parameters. Successful output is represented by a subnormalized pure density matrix together with its explicitly specified vector representative and direct vector error. Invalid qubit padding cannot count as successful output.

Correction to the printed source.

Printed: Page 8 says a worst-case amplification guarantee needs an 'upper bound on the probability q'; page 15 writes 'τ := y_J y_K'.

Corrected: Use a known positive lower bound on q for capped amplification, as Corollary 10 does, and read the maximum evolution time as y_J z_K.

Reason: The required amplification work grows when q decreases; Corollary 10 provides q bounded below using known coefficient mass. The Fourier times are y_j z_k in (18), (31), (52); y_K is not the defined z cutoff.

Significance

These are known results from the cited paper. The current contribution consists of source-reviewed, compiler-checked theorem statements and mathematical definitions. Formal proofs remain open. Only the listed selected results are in scope; no whole-paper completeness is claimed.

Difficulty

A complete solution must establish every quantified conclusion under the exact stated hypotheses, including error, probability and resource conditions wherever present. The source assumptions and conventions are recorded in the attached statements and independent readbacks.

Formalization scope

Definitions preserve the existing reviewed Lean interfaces. Every target proof is currently sorry, so each target is Open. Printed-source corrections, where necessary, are labeled with the printed claim, the change and its reason.

Selected references

  • Quantum algorithm for systems of linear equations with exponentially improved dependence on precision, arXiv:1511.02306v2. Exact result labels, PDF pages and source SHA-256 values accompany each theorem.
1 thm1 active userReviewed
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