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Each mission turns a result from a paper or textbook into small Lean 4 statements anyone can tackle.

Campaigns (experimental)

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.

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About Prove2Me

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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Each mission turns a result from a paper or textbook into small Lean 4 statements anyone can tackle.

Campaigns (experimental)

See all campaigns →

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.

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.

≥ 2.131121719190Formalized record→≥ 2.15Open frontier
9 provers on it18 of 19 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
4 provers on it7 of 8 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.

≤ 7.101862832357Formalized record→≤ 2Open frontier
17 provers on it8 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.
≤ 21Formalized record→≤ 16Open frontier
5 provers on it12 of 13 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.

≤ 25Formalized record→≤ 5Open frontier
38 provers on it14 of 16 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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About Prove2Me

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.

How Prove2Me worksResearch paper
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Quantum Information·Captain: Goku

Lie-Semigroup Structures for Reachability and Control of Open Quantum SystemsResearch Paper

Motivation

In view of controlling finite dimensional open quantum systems, we provide a unified Lie-semigroup framework describing the structure of completely positive trace-preserving maps. It allows (i) to identify the Kossakowski-Lindblad generators as the Lie wedge of a subsemigroup, (ii) to link properties of Lie semigroups such as divisibility with Markov properties of quantum channels, and (iii) to characterise reachable sets and controllability in open systems. We elucidate when time-optimal controls derived for the analogous closed system already give good fidelities in open systems and when a more detailed knowledge of the open system (e.g., in terms of the parameters of its Kossakowski-Lindblad master equation) is actually required for state-of-the-art optimal-control algorithms. -- As an outlook, we sketch the structure of a new, potentially more efficient numerical approach explicitly making use of the corresponding Lie wedge.

This mission is the statement-level formalization of Lie-Semigroup Structures for Reachability and Control of Open Quantum Systems (arXiv:0811.3906v4). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

5 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is The generated Markovian semigroup has the full channel tangent wedge (Theorem III.3, PDF p. 8). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Deferred results

30 results of the paper are not stated yet, because the library lacks an interface they need:

  • Lemma II.1: Accepted source-matched theorem for Lemma II.1 (provenance boundary) (hard)
  • Theorem II.1: Missing Ad_K invariance of c (source-ambiguity)
  • Proposition II.1: Accepted source-matched theorem for Proposition II.1 (provenance boundary) (hard)
  • Proposition II.2: Accepted source-matched theorem for Proposition II.2 (provenance boundary) (hard)
  • Theorem II.2: Accepted source-matched theorem for Theorem II.2 (provenance boundary) (hard)
  • Theorem II.3: Accepted source-matched theorem for Theorem II.3 (provenance boundary) (hard)
  • Theorem II.4: Accepted source-matched theorem for Theorem II.4 (provenance boundary) (hard)
  • Theorem II.5: Accepted source-matched theorem for Theorem II.5 (provenance boundary) (hard)
  • Theorem II.6: Accepted source-matched theorem for Theorem II.6 (provenance boundary) (hard)
  • Corollary II.1: Accepted source-matched theorem for Corollary II.1 (provenance boundary) (hard)
  • Corollary II.2: Accepted source-matched theorem for Corollary II.2 (provenance boundary) (hard)
  • Theorem III.1: Independent x/y control indexing and original-result provenance (source-ambiguity)
  • Theorem III.2: Accepted source-matched theorem for Theorem III.2 (provenance boundary) (hard)
  • Proposition III.1: Accepted source-matched theorem for Proposition III.1 (provenance boundary) (hard)
  • Theorem III.4: Dimension-qualified nondivisibility theorem (source-ambiguity)
  • Corollary III.2: Dimension-qualified failure of Lie-subsemigroup generation (source-ambiguity)
  • Corollary III.3: Dimension-qualified local failures and non-semialgebra wedge (source-ambiguity)
  • Corollary III.4: Nonvacuous fixed-semigroup identity neighborhood and generator signs (source-ambiguity)
  • Corollary III.5: Endpoint representations versus one fixed exponential trajectory (source-ambiguity)
  • Resume: A specified genericity space and canonical dissipator gauge (source-ambiguity)
  • Proposition III.2: Nontrivial homogeneous space for the smallest-positive-scaling conclusion (source-ambiguity)
  • Corollary III.6: Canonical dissipator gauge and a definition of generic (source-ambiguity)
  • Reachability-product: Accepted source-matched theorem for Reachability-product (provenance boundary) (hard)
  • Remark II.1: Accepted source-matched theorem for Remark II.1 (provenance boundary) (hard)
  • Remark II.3: Accepted source-matched theorem for Remark II.3 (provenance boundary) (hard)
  • Trace-norm-contraction: Accepted source-matched theorem for Trace-norm-contraction (provenance boundary) (hard)
  • Purity-unitality: Accepted source-matched theorem for Purity-unitality (provenance boundary) (hard)
  • Remark III.1: Accepted source-matched theorem for Remark III.1 (provenance boundary) (hard)
  • Markovian-stratification: Dimension scope and explicit interior/strict-inclusion witnesses (source-ambiguity)
  • Scalar-decay-optimal-time: Quantitative almost-uniform decay and attained argmax domain (source-ambiguity)

Selected references

  • Lie-Semigroup Structures for Reachability and Control of Open Quantum Systems, arXiv:0811.3906v4, https://arxiv.org/abs/0811.3906v4
8 thms1 active userReviewed
Quantum Information·Captain: Goku

Classical Capacity of Single-Mode Bosonic Gaussian ChannelsResearch Paper

Motivation

The classical capacity of a noisy optical channel is the maximum rate at which information can be transmitted reliably, given a constraint on the mean input energy. For the ubiquitous bosonic Gaussian channels, which include standard models of loss and noise in fibre and free-space optical links, determining this rate requires addressing whether entanglement between channel uses or non-Gaussian signals can outperform Gaussian encodings. More precisely, the question is whether the energy-constrained Holevo information is additive across arbitrarily many channel uses and coincides with its Gaussian counterpart. We answer these fundamental questions in the affirmative for every single-mode bosonic Gaussian channel at every input energy. Namely, we prove that independently prepared Gaussian states with Gaussian-distributed random displacements achieve the capacity, including in the low-energy regime where squeezing the signals competes with encoding information in their displacement. Our proof connects an entanglement inequality to a sharp, additive lower bound on output entropy. We then characterise communication above capacity: under a strict total photon-number cutoff, the probability of correct decoding decreases exponentially with the number of channel uses, and we derive explicit bounds on the decay exponent. When only the mean photon number is constrained, a simple energy-rescaling formula determines exactly the entire asymptotic rate--error trade-off: the capacity at mean photon number NNN and allowed average decoding error εεε equals the vanishing-error capacity at mean photon number N/(1−ε)N/(1-ε)N/(1−ε). Together, these results identify the ultimate limits of classical communication for some of the most fundamental models of optical communication. △ Less

This mission is the statement-level formalization of Classical Capacity of Single-Mode Bosonic Gaussian Channels (arXiv:2610.22308v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

2 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Affine envelope and joint convexity of the moment-resolved entropy (Eq. (18), PDF p. 4). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Deferred results

27 results of the paper are not stated yet, because the library lacks an interface they need:

  • Corollary 3 (pp.5,12), resolving the p.1 paper-result seed: capacities and water-filling: bosonic channels, arbitrary probability ensembles, Gaussian displacement ensembles, and operational classical capacity (hard)
  • Theorem 1: output entropy from second moments: finite-energy Fock states, raw quadrature quadratic-form moments, von Neumann entropy, and squeezed vacua (hard)
  • Theorem 2: moment-resolved Gaussian optimality: continuous bosonic ensembles and product Gaussian displacement ensembles (hard)
  • Corollary 4: finite correlated blocks: passive Fock-space implementation of a common noise diagonalizer and repeated-block capacity (hard)
  • Unnumbered §IV: positive mode costs and marginal-gain rule: weighted-energy bosonic ensemble capacity and actual Gaussian Holevo energy functions (hard)
  • Unnumbered Eq.(22) and Appendix E.1: operational limit of chain memory channels: growing chain Gaussian channels and operational coding capacity along a nonidentical sequence (hard)
  • Proposition 5: tight Gaussian reference: infinite-dimensional relative entropy and a constructed optimal Gaussian reference (hard)
  • Unnumbered Eq.(24), Appendix F: uniqueness and quantitative stability: bosonic ensemble Holevo deficit, trace norm, marginals and Gaussian reference tensor powers (hard)
  • Theorem 6: exact nonzero-error capacity: operational nonzero-error capacity for bosonic mean-energy code sequences (hard)
  • Proposition 7: exponential cutoff strong converse: bosonic photon-cutoff codes and their operational capacity (hard)
  • Proposition 8: mixed-state affine entropy bound: mixed bosonic bipartite states and unbounded annihilation-operator quadratic forms (hard)
  • Lemma 9: quadrature-dependent dilation expectation: symplectic Fock unitaries, their Stinespring action, and quadrature-dependent quadratic-form expectations (hard)
  • Proposition 10: growing-memory converse and error trade-off: uniform Gaussian dilations and operational codes along growing memory blocks (hard)
  • Fact 11: Gaussification commutes with Gaussian channels: Gaussification as an actual normalized Gaussian Fock state with prescribed moments (hard)
  • Proposition 12: transfer from cutoff to mean energy: arbitrary bosonic-input channels, bounded decoding POVMs, and cutoff-code success supremum (hard)
  • Lemma 13: energy-preserving positive-filter coding inequality: Stinespring image filters and projective operator tensor norm on infinite Fock factors (hard)
  • Lemma 14: uniform exponential moments for symplectic unitaries: symplectic unitary tensor powers and extended nonnegative photon-exponential expectations (hard)
  • Proposition 15: approximating energy image filters: positive finite-rank energy-image filters and finite-local-support approximants on Fock tensor factors (hard)
  • Proposition 16: computable filter exponent: actual cutoff-code success exponent, Gaussian dilation constants and true capacity function (hard)
  • Proposition 17: explicit photon-tail bound: canonical Gaussian channel outputs on arbitrary cutoff states and decoding success (hard)
  • Lemma 18: output photon-number moments: extended output photon-number moments for arbitrary entangled cutoff Fock states (hard)
  • Proposition 19: converse for optimal Gaussian signal family: actual displaced squeezed Gaussian codewords and infinite-dimensional Petz Renyi expressions (hard)
  • Unnumbered Appendix B: energy-preserving canonical reduction: Fock implementations of input phase rotations and output symplectic transformations (hard)
  • Unnumbered G8: photon-subspace dimension and channel-independent bound: photon-subspace Hilbert dimension and channel-independent cutoff decoding success (hard)
  • Unnumbered H44: approach of the filter exponent to capacity: dilation-dependent H43 filter exponent using true operational Gaussian capacity (hard)
  • Unnumbered H45: weak photon tails: averaged photon-tail weight, actual cutoff-code supremum and vacuum-mixture code sequence (hard)
  • Unnumbered H46–H47: fixed multimode Gaussian channels: fixed finite-mode Gaussian channels and regularized operational bosonic capacity (hard)

Selected references

  • Classical Capacity of Single-Mode Bosonic Gaussian Channels, arXiv:2610.22308v1, https://arxiv.org/abs/2610.22308v1
3 thms1 active userReviewed
Quantum Information·Captain: Goku

Entanglement-breaking channels in infinite dimensionsResearch Paper

Motivation

We give a representation for entanglement-breaking channels in separable Hilbert space that generalizes the "Kraus decomposition with rank one operators" and use it to describe the complementary channels. We also give necessary and sufficient condition of entanglement-breaking for a general quantum Gaussian channel. Application of this condition to one-mode channels provides several new cases where the additivity conjecture holds in full generality.

This mission is the statement-level formalization of Entanglement-breaking channels in infinite dimensions (arXiv:0802.0235v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

4 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Radon–Nikodym representation of a POVM (Lemma 1: Radon–Nikodym representation of a POVM (9)–(10), PDF p. 3). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Deferred results

18 results of the paper are not stated yet, because the library lacks an interface they need:

  • Theorem 2: Gaussian entanglement-breaking criterion and representation (30)–(31): Normal Gaussian trace-class channels, Gaussian states and trace-norm measure-and-prepare integral (hard)
  • Theorem 1: continuous densely defined rank-one representation (17)–(18): Measurable trace-class preparation from densely defined algebraic functionals (hard)
  • Proposition 1: sign of coherent information for (anti-)degradable channels: Genuine complementary trace-class channels and finite-entropy coherent information (hard)
  • Unnumbered: explicit Stinespring isometry and complementary kernel: Vector-valued L2 Stinespring realization and scalar integral-operator kernel (hard)
  • Example: spectral L2 measure-and-prepare channel and complementary Schur kernel: Canonical trace-class L2 diagonal and spectral measure-and-prepare map (hard)
  • Unnumbered: every entanglement-breaking channel is anti-degradable: Explicit entanglement-breaking antidegrading map on the full L2 environment trace class (hard)
  • Unnumbered: sharp Gaussian observable iff noise vanishes: Joint spectral measure of unbounded commuting quadratures with symplectic outcome transport (hard)
  • Proposition 2: covariant operator density of a nonsingular Gaussian observable: Gaussian trace-class seed state and displaced covariant operator density (hard)
  • Proposition 3: explicit Gaussian Naimark dilation (24)–(26): Gaussian ancillary Weyl system, normal partial-state evaluation and sharp joint spectral dilation (hard)
  • Unnumbered: complete positivity condition for Gaussian channel parameters (29): Normal trace-class realization of the Weyl channel characteristic law (hard)
  • Unnumbered: necessary PPT inequalities and Gaussian output PPT property (35): Partial transpose and Gaussian state law on a completed reference tensor product (hard)
  • Unnumbered: isotropic K gives a sharp-measurement c-q channel: Sharp quadrature PVM and displaced Gaussian preparation channel (hard)
  • Unnumbered claim: arbitrary sharp peaking around every outcome point: Correct outcome range in the arbitrary sharp-peaking claim (source-ambiguity)
  • Unnumbered: complete one-mode entanglement-breaking thresholds A, B1, B2, C, D: Actual canonical Gaussian channels and Gaussian unitary equivalence (hard)
  • Unnumbered: constrained chi-capacity additivity for the classified one-mode regimes: Extended constrained Holevo capacity for generalized ensembles and channel tensor products (hard)
  • Unnumbered: entanglement-breaking channels have zero quantum capacity: Operational unconstrained quantum capacity on separable trace-class channels (hard)
  • Unnumbered: energy-constrained tensor-power additivity and single-letter classical capacity (8): Formal spectral-energy constraints, tensor-power classical codes and extended constrained Holevo capacity on full trace-class channels (hard)
  • Unnumbered conditional discussion: Gaussian-optimizer capacity formula: Scope of the Gaussian optimizer conjecture used for operational capacity (source-ambiguity)

Selected references

  • Entanglement-breaking channels in infinite dimensions, arXiv:0802.0235v1, https://arxiv.org/abs/0802.0235v1
6 thms1 active userReviewed
Quantum Information·Captain: Goku

Mutual and coherent informations for infinite-dimensional quantum channelsResearch Paper

Motivation

The work is devoted to study of quantum mutual information and coherent information -- the two important characteristics of quantum communication channel. Appropriate definitions of these quantities in the infinite-dimensional case are given and their properties are studied in detail. Basic identities relating quantum mutual information and coherent information of a pair of complementary channels are proved. An unexpected continuity property of quantum mutual information and coherent information following from the above identities is observed. An upper bound for the coherent information is obtained.

This mission is the statement-level formalization of Mutual and coherent informations for infinite-dimensional quantum channels (arXiv:1004.2495v2). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

24 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Theorem 1: complementary-channel mutual-information identity (22) (Theorem 1: complementary-channel mutual-information identity (22), PDF p. 13). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Selected references

  • Mutual and coherent informations for infinite-dimensional quantum channels, arXiv:1004.2495v2, https://arxiv.org/abs/1004.2495v2
27 thms1 active userReviewed
Quantum Information·Captain: Goku

Squashed entanglement in infinite dimensionsResearch Paper

Motivation

We analyse two possible definitions of the squashed entanglement in an infinite-dimensional bipartite system: direct translation of the finite-dimensional definition and its universal extension. It is shown that the both definitions produce the same lower semicontinuous entanglement measure possessing all basis properties of the squashed entanglement on the set of states having at least one finite marginal entropy. Is also shown that the second definition gives an adequate extension of this measure to the set of all states of infinite-dimensional bipartite system. A general condition relating continuity of the squashed entanglement to continuity of the quantum mutual information is proved and its corollaries are considered. Continuity bound for the squashed entanglement under the energy constraint on one subsystem is obtained by using the tight continuity bound for conditional mutual information (proved in the Appendix by using Winter's technique). It is shown that the same continuity bound is valid for the entanglement of formation. As a result the asymptotic continuity of the both entanglement measures under the energy constraint on one subsystem is proved.

This mission is the statement-level formalization of Squashed entanglement in infinite dimensions (arXiv:1507.08964v5). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

2 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Compactness of bipartite states from both marginal sets (Lemma 1, PDF p. 4). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Deferred results

25 results of the paper are not stated yet, because the library lacks an interface they need:

  • Lemma 3: contraction bound for MI and conditional entropy: Homogeneous extended spectral entropy and MI; finite-first-marginal conditional entropy; contraction conjugation (hard)
  • Proposition 1 A–C: universal extension of continuous monotones: Coherent finite-system monotone families, general quantum instruments, finite-rank compressions and EM1–EM8 (hard)
  • Corollary 1: universal entanglement of formation is the continuous convex roof: Continuous pure-state convex roof and universal finite-rank formation extension (hard)
  • Unnumbered consequence after Corollary 1: formation equality iff lower semicontinuity: Discrete and continuous formation roofs as actual extended-valued functions (hard)
  • Lemma 4 A–B: finite versus infinite extension systems: Extended MI, finite-projection CQMI, direct and finite-ancilla squashed infima (hard)
  • Unnumbered consequence of Lemma 4: criterion for finite-ancilla and direct functions to coincide: Globally defined direct and finite-ancilla squashed functions (hard)
  • Proposition 2 A–D: properties of direct infinite-dimensional squashed entanglement: Full direct squashed-entanglement function, EM2–EM8 and entropy-restricted trace-norm topology (hard)
  • Proposition 2A literal convex-hull scope (deferred source ambiguity): Literal Proposition 2A convex-hull scope (source-ambiguity)
  • Lemma 5: contraction and postselection bounds for CQMI: Homogeneous extended CQMI, contraction filtering, and positive-trace postselection (hard)
  • Abstract main result pinned to Proposition 3 A–D: universal squashed entanglement: Universal squashed extension and exact entanglement-measure predicates (hard)
  • Corollary 2: squashed entanglement is bounded by the corresponding formation roof: Both squashed functions and both formation roofs on full state spaces (hard)
  • Proposition 4 A–C: continuity equivalences and dominated convergence: Extended-valued MI and all squashed variants with sequential topology and uniform finite-ancilla gaps (hard)
  • Lemma 6 A–B: lower semicontinuity and continuity of bounded-ancilla functions (normalization correction): Bounded-ancilla squashed function and correctly normalized extended liminf gaps (hard)
  • Lemma 7: MI continuity implies upper semicontinuity of direct E_sq: Direct squashed-entanglement function and extended MI along arbitrary trace-norm sequences (hard)
  • Corollary 3: preservation of the continuity conditions by local operations: Trace-nonincreasing CP local operations and eventual normalized output sequences (hard)
  • Corollary 4: dominated local images of the limiting state: Local quantum operations, operator domination and squashed continuity (hard)
  • Corollary 5: one finite subsystem and explicit continuity modulus: All squashed variants with one arbitrary infinite subsystem (hard)
  • Corollary 6 A–C: energy-constrained equality and continuity: Extended one-marginal energy expectation, partition trace and both pairs of entanglement functions (hard)
  • Proposition 5: common energy-constrained continuity bound for E_sq and E_F: Actual Gibbs maximizer, form-energy state domain and both entanglement measures (hard)
  • Remark 4: uniform continuity of both energy-constrained entanglement measures: Real-valued entanglement restrictions to the full form-energy set with trace-norm uniformity (hard)
  • Corollary 7: asymptotic continuity under an A-only mean-energy bound: Correlated tensor-power density states, sum Hamiltonian form energy and normalized entanglement differences (hard)
  • Lemma 8 (Appendix): energy-constrained CQMI continuity bound: Arbitrary-state extended CQMI and one-marginal form-energy/Gibbs interfaces (hard)
  • Remark 5: uniform continuity of CQMI under an A-only energy bound: Trace-norm uniform structure and finite real CQMI on the A-only energy set (hard)
  • Remark 6: oscillator leading term and informal asymptotic tightness: Quantified full oscillator CQMI bound and asymptotic-tightness regime (source-ambiguity)
  • Remark 6: explicit mixed-state witnesses for the CQMI lower modulus: Actual mixed Gibbs states, pure-state purification and extended CQMI on flagged mixtures (hard)

Selected references

  • Squashed entanglement in infinite dimensions, arXiv:1507.08964v5, https://arxiv.org/abs/1507.08964v5
4 thms1 active userReviewed
Quantum Information·Captain: Goku

One-mode quantum Gaussian channelsResearch Paper

Motivation

A classification of one-mode Gaussian channels is given up to canonical unitary equivalence. A complementary to the quantum channel with additive classical Gaussian noise is described providing an example of one-mode Gaussian channel which is neither degradable nor anti-degradable.

This mission is the statement-level formalization of One-mode quantum Gaussian channels (arXiv:quant-ph/0607051v2). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

2 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Six canonical forms of one-mode Gaussian channels after displacement removal (§1, unnumbered Theorem, pp.2–4, PDF p. 2). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Deferred results

15 results of the paper are not stated yet, because the library lacks an interface they need:

  • §2 A1, pp.4–5: thermal replacer and swap-dilation weak complement (hard)
  • §2 A2, (6)–(7): the actual A2 mixed-thermal dilation and its environment channel (hard)
  • §2 B1, Gaussian covariance and entropy calculation: actual diagonal Gaussian input densities, pure-dilation outputs and spectral entropy (hard)
  • §2 B1, degradability and infinite capacity: operational unconstrained quantum capacity and a genuine degrading normal channel (hard)
  • §2 C, attenuation/amplification models: mixed-thermal attenuation/amplification joint dilations and additive-noise composition (hard)
  • §2 D, phase conjugation model: the actual phase-conjugating dilation as an amplifier weak complement (hard)
  • §3, (8)–(9): trace-norm Gaussian displacement integration for every trace-class input (hard)
  • §3, (10)–(11): H-valued weighted-L2 unitary, both partial traces and the actual complementary kernel (hard)
  • §3, (12)–(14): self-adjoint environmental generators and CCR with legitimate domains (hard)
  • §3, (15)–(16) and six generator outputs: joint system/ancilla conjugation and domain-correct canonical dynamics (hard)
  • §3, (17), proof pp.9–10: the actual all-input additive-noise complementary channel (hard)
  • §3, complementary covariance and four eigenvalues: actual thermal complementary output covariance tied to its four spectral values (hard)
  • §3, (18)–(19): infinite-dimensional spectral entropy and exchange entropy of actual output densities (hard)
  • §3, F(N), vacuum value and limit: thermal coherent information linked to actual channel entropies (hard)
  • §3, Nc=0.99 exp(-1), also p.7: two operational positive capacities and normal-channel (anti)degradability (hard)

Selected references

  • One-mode quantum Gaussian channels, arXiv:quant-ph/0607051v2, https://arxiv.org/abs/quant-ph/0607051v2
4 thms1 active userReviewed
Quantum Information·Captain: Goku

Separability and Entanglement-Breaking in Infinite DimensionsResearch Paper

Motivation

In this paper we give a general integral representation for separable states in the tensor product of infinite dimensional Hilbert spaces and provide the first example of separable states that are not countably decomposable. We also prove the structure theorem for the quantum communication channels that are entanglement-breaking, generalizing the finite-dimensional result of M. Horodecki, Ruskai and Shor. In the finite dimensional case such channels can be characterized as having the Kraus representation with operators of rank 1. The above example implies existence of infinite-dimensional entanglement-breaking channels having no such representation.

This mission is the statement-level formalization of Separability and Entanglement-Breaking in Infinite Dimensions (arXiv:quant-ph/0504204v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

6 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Separable states are precisely probability mixtures of product states (§2, equation (2), PDF p. 2). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Deferred results

9 results of the paper are not stated yet, because the library lacks an interface they need:

  • Theorem 1: A valid compactness statement for the printed arbitrary set P (source-ambiguity)
  • Theorem 2: Normalized weakly countably additive POVM on an arbitrary complete separable metric outcome space and its trace-pairing probability laws (hard)
  • §3, paragraph after Theorem 2: Countable weak-effect and trace-norm rank-one Kraus sums, plus the constructed faithful-reference state (9) (hard)
  • §3, unnumbered existence result: A genuine infinite-dimensional channel witness and the exact countable rank-one Kraus predicate (hard)
  • §4, equations (12)–(14): The position spectral measure E(B), canonical L¹ diagonal density, and the fixed channel (12) (hard)
  • Conjecture: A proof of density of W in all separable states (source-ambiguity)
  • Theorem 4, equations (20)–(21): Infinite-dimensional extended Umegaki relative entropy, finite-ensemble Holevo capacity, and the channel (12) (hard)
  • Theorem 4 proof, equations (22)–(23): The exact range of the constructed rotation channel (12) on all states and all L¹ probability densities (hard)
  • Theorem 4 proof, finite-entropy conclusion: Extended von Neumann entropy on arbitrary trace-class states and its trace-norm restriction to the closed output range (hard)

Selected references

  • Separability and Entanglement-Breaking in Infinite Dimensions, arXiv:quant-ph/0504204v1, https://arxiv.org/abs/quant-ph/0504204v1
8 thms1 active userReviewed
Quantum Information·Captain: Goku

Trading classical communication, quantum communication, and entanglement in quantum Shannon theoryResearch Paper

Motivation

We give trade-offs between classical communication, quantum communication, and entanglement for processing information in the Shannon-theoretic setting. We first prove a unit-resource capacity theorem that applies to the scenario where only the above three noiseless resources are available for consumption or generation. The optimal strategy mixes the three fundamental protocols of teleportation, super-dense coding, and entanglement distribution. We then provide an achievable rate region and a matching multi-letter converse for the direct static capacity theorem. This theorem applies to the scenario where a large number of copies of a noisy bipartite state are available (in addition to consumption or generation of the above three noiseless resources). Our coding strategy involves a protocol that we name the classically-assisted state redistribution protocol and the three fundamental protocols. We finally provide an achievable rate region and a matching mutli-letter converse for the direct dynamic capacity theorem. This theorem applies to the scenario where a large number of uses of a noisy quantum channel are available in addition to the consumption or generation of the three noiseless resources. Our coding strategy combines the classically-enhanced father protocol with the three fundamental unit protocols.

This mission is the statement-level formalization of Trading classical communication, quantum communication, and entanglement in quantum Shannon theory (arXiv:0901.3038v3). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

1 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Finite-block converse with explicit continuity corrections and a common classical refinement (Appendix F, (106)–(107), and both proof chains on PDF p.25, PDF p. 24). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Deferred results

14 results of the paper are not stated yet, because the library lacks an interface they need:

  • Theorem 1: unit resource capacity region: Operational simultaneous signed unit-resource conversion region (hard)
  • Theorem 2: direct static capacity theorem: Operational static conversion region and full regularized CASR union (hard)
  • Theorem 3: direct dynamic capacity theorem: Operational dynamic three-resource region and full regularized CEF union (hard)
  • Lemma 1: classically-assisted quantum state redistribution: Operational static primitive achievability for a remote instrument (hard)
  • Corollary 4: grandmother resource inequality: Operational entanglement-distillation rates with both communication costs (hard)
  • Lemma 3: additivity inclusion with a noiseless entangled state: Static operational helper families at all real ebit rates (hard)
  • Lemma 4: additivity inclusion with a noiseless quantum channel: Dynamic operational helper families at all real forward-qubit rates (hard)
  • Lemma 5: additivity inclusion with a noiseless entangled state: Static operational helper families in the noisy-teleportation quadrant (hard)
  • Lemma 6: additivity inclusion with a noiseless quantum channel: Dynamic operational helper families in the assisted entanglement quadrant (hard)
  • §VIII.A: erased-state optimal trade-off and single-letterization: A valid all-parameter erased-state optimal boundary (source-ambiguity)
  • §VIII.B: dephasing full dynamic single-letterization: Operational dephasing capacity and unrestricted one-copy CEF state union (hard)
  • §VII.C: benefit of coding with charged classical communication: Operational positive assisted capacity and the two closed wasting-allowed strategy regions (hard)
  • §VII.C: claimed constant excess ebit cost: The target-rate domain and optimization convention for a constant entanglement-cost difference (source-ambiguity)
  • Appendix A, (85)–(88): displayed finite-block static converse: A consistently scaled finite-block static converse with explicit error terms (source-ambiguity)

Selected references

  • Trading classical communication, quantum communication, and entanglement in quantum Shannon theory, arXiv:0901.3038v3, https://arxiv.org/abs/0901.3038v3
5 thms1 active userReviewed
Machine LearningOptimizationStatistics·Captain: mikedeng1

High-Dimensional Learning Under Approximate Sparsity with Applications to Nonsmooth Estimation and Regularized Neural Networks: Excess-Risk Bounds at S3ONC Solutions of MCP-Regularized M-EstimationResearch Paper

Motivation

High-dimensional statistical learning (HDSL) fits a model with ppp parameters from nnn samples when ppp may far exceed nnn. The standard guarantees for sparse estimators, such as the Lasso, rest on restricted strong convexity (RSC) or restricted eigenvalue conditions on the empirical risk (Negahban et al., 2012; Loh & Wainwright, 2015). These conditions fail or are hard to verify for many losses that matter in operations research and machine learning: nonsmooth losses, losses of neural networks, and M-estimation problems whose population risk is not strongly convex near any sparse vector.

Liu, Ye and Lee (arXiv:1903.00616v2; Operations Research, 2022) remove RSC entirely. They regularize the empirical risk with a folded concave penalty, the minimax concave penalty (MCP) of Zhang (2010), and analyse not a global minimizer (intractable, since the problem is nonconvex) but any point satisfying a weak second-order stationarity condition. They also replace exact sparsity by approximate sparsity: the best sparse vector need only be εA\varepsilon_AεA​-optimal for the population risk. Their main result, Theorem 1, gives an excess-risk bound whose sample complexity is poly-logarithmic in ppp.

Setting

Observations Z1,…,ZnZ_1, \dots, Z_nZ1​,…,Zn​ are i.i.d. copies of a random element ZZZ of a measurable space W\mathcal WW. A loss L(β,z)L(\beta, z)L(β,z), with parameter β∈Rp\beta \in \mathbb R^pβ∈Rp, defines the population risk L(β)=E[L(β,Z)]\mathbb L(\beta) = \mathbb E[L(\beta, Z)]L(β)=E[L(β,Z)], assumed finite for every β\betaβ and bounded below, the empirical risk Ln(β)=1n∑iL(β,Zi)\mathcal L_n(\beta) = \frac1n\sum_i L(\beta, Z_i)Ln​(β)=n1​∑i​L(β,Zi​), and the regularized objective

Ln,λ(β)=Ln(β)+∑j=1pPλ(∣βj∣),Pλ(θ)=∫0θ[aλ−t]+a dt,\mathcal L_{n,\lambda}(\beta) = \mathcal L_n(\beta) + \sum_{j=1}^p P_\lambda(|\beta_j|), \qquad P_\lambda(\theta) = \int_0^\theta \frac{[a\lambda - t]_+}{a}\,dt,Ln,λ​(β)=Ln​(β)+j=1∑p​Pλ​(∣βj​∣),Pλ​(θ)=∫0θ​a[aλ−t]+​​dt,

with tuning parameters a,λ>0a, \lambda > 0a,λ>0. Norms: ∥⋅∥\|\cdot\|∥⋅∥ is Euclidean, ∣⋅∣|\cdot|∣⋅∣ is ℓ1\ell_1ℓ1​, ∥⋅∥∞\|\cdot\|_\infty∥⋅∥∞​ is the max norm and ∥⋅∥0\|\cdot\|_0∥⋅∥0​ counts nonzero entries.

The standing assumptions are:

  • smoothness (11): each partial derivative ∂L/∂βj\partial L/\partial\beta_j∂L/∂βj​ is ULU_LUL​-Lipschitz along coordinate jjj, for almost every zzz;
  • Assumption 3: the centred losses L(β,Zi)−EL(β,Zi)L(\beta, Z_i) - \mathbb E L(\beta, Z_i)L(β,Zi​)−EL(β,Zi​) are sub-exponential with ψ1\psi_1ψ1​-norm at most σ≥1\sigma \ge 1σ≥1 on the box ∥β∥∞≤R\|\beta\|_\infty \le R∥β∥∞​≤R;
  • Assumption 4: L(⋅,z)L(\cdot, z)L(⋅,z) is C(z)\mathcal C(z)C(z)-Lipschitz on the box, where C(Zi)\mathcal C(Z_i)C(Zi​) is sub-exponential around its mean (ψ1\psi_1ψ1​-norm at most σL≥1\sigma_L \ge 1σL​≥1) and E C(Zi)≤Cμ\mathbb E\,\mathcal C(Z_i) \le \mathcal C_\muEC(Zi​)≤Cμ​, Cμ≥1\mathcal C_\mu \ge 1Cμ​≥1;
  • Assumption 1 (A-sparsity): some βεA∗\beta^*_{\varepsilon_A}βεA​∗​ with ∥βεA∗∥∞≤R\|\beta^*_{\varepsilon_A}\|_\infty \le R∥βεA​∗​∥∞​≤R, R≥1R \ge 1R≥1, and s=∥βεA∗∥0>1s = \|\beta^*_{\varepsilon_A}\|_0 > 1s=∥βεA​∗​∥0​>1 nonzero entries satisfies L(βεA∗)−inf⁡βL(β)≤εA\mathbb L(\beta^*_{\varepsilon_A}) - \inf_\beta \mathbb L(\beta) \le \varepsilon_AL(βεA​∗​)−infβ​L(β)≤εA​. Assumption 2 replaces inf⁡βL\inf_\beta \mathbb Linfβ​L by any lower bound Lg∗L^*_gLg∗​.

A vector β^\hat\betaβ^​ satisfies the S³ONC (significant subspace second-order necessary conditions, Definition 1) at a sample if it is a KKT point of Ln,λ\mathcal L_{n,\lambda}Ln,λ​, with subgradients κj∈∂∣β^j∣\kappa_j \in \partial|\hat\beta_j|κj​∈∂∣β^​j​∣, and UL+Pλ′′(∣β^j∣)≥0U_L + P''_\lambda(|\hat\beta_j|) \ge 0UL​+Pλ′′​(∣β^​j​∣)≥0 whenever ∣β^j∣∈(0,aλ)|\hat\beta_j| \in (0, a\lambda)∣β^​j​∣∈(0,aλ). With ζ~=ln⁡(3eR(σL+Cμ))\tilde\zeta = \ln(3eR(\sigma_L + \mathcal C_\mu))ζ~​=ln(3eR(σL​+Cμ​)), Theorem 1 fixes λ=8σ/(can2/3) [ln⁡(n2/3p)+ζ~]\lambda = \sqrt{8\sigma/(c a n^{2/3})\,[\ln(n^{2/3}p) + \tilde\zeta]}λ=8σ/(can2/3)[ln(n2/3p)+ζ~​]​, where c∈(0,1/2]c \in (0, 1/2]c∈(0,1/2] is the constant of the Bernstein inequality (12).

Formalization targets

Goal: Theorem 1 (p. 18)

For a<min⁡{1/UL,1}a < \min\{1/U_L, 1\}a<min{1/UL​,1} and any random β^\hat\betaβ^​ with ∥β^∥∞≤R\|\hat\beta\|_\infty \le R∥β^​∥∞​≤R satisfying the S³ONC almost surely:

(i) if Ln,λ(β^)≤Ln,λ(βεA∗)+Γ\mathcal L_{n,\lambda}(\hat\beta) \le \mathcal L_{n,\lambda}(\beta^*_{\varepsilon_A}) + \GammaLn,λ​(β^​)≤Ln,λ​(βεA​∗​)+Γ almost surely and n>C3[((Γ+εA)/σ)3+s(ln⁡(np)+ζ~)]n > C_3[((\Gamma + \varepsilon_A)/\sigma)^3 + s(\ln(np) + \tilde\zeta)]n>C3​[((Γ+εA​)/σ)3+s(ln(np)+ζ~​)], then with probability at least 1−2(p+1)e−n/C3−6e−n1/3/C31 - 2(p+1)e^{-n/C_3} - 6e^{-n^{1/3}/C_3}1−2(p+1)e−n/C3​−6e−n1/3/C3​,

L(β^)−inf⁡βL(β)≤C3σ[s(ln⁡(np)+ζ~)n2/3+s(ln⁡(np)+ζ~)n+1n1/3]+C3σ(Γ+εA)n1/3+Γ+εA;\mathbb L(\hat\beta) - \inf_\beta \mathbb L(\beta) \le C_3\sigma\Big[\frac{s(\ln(np)+\tilde\zeta)}{n^{2/3}} + \sqrt{\frac{s(\ln(np)+\tilde\zeta)}{n}} + \frac{1}{n^{1/3}}\Big] + C_3\sqrt{\frac{\sigma(\Gamma+\varepsilon_A)}{n^{1/3}}} + \Gamma + \varepsilon_A;L(β^​)−βinf​L(β)≤C3​σ[n2/3s(ln(np)+ζ~​)​+ns(ln(np)+ζ~​)​​+n1/31​]+C3​n1/3σ(Γ+εA​)​​+Γ+εA​;

(ii) if β^\hat\betaβ^​ is no worse in Ln,λ\mathcal L_{n,\lambda}Ln,λ​ than a Lasso solution β^ℓ1\hat\beta^{\ell_1}β^​ℓ1​, the Γ\GammaΓ-free bound (22) holds under (21).

C3,C4C_3, C_4C3​,C4​ are universal constants. The goal fixes the polynomial rate n−1/3n^{-1/3}n−1/3; the general-rate result is Proposition 1.

Milestones (the paper's proof chain)

  1. Proposition 2: the S³ONC forces ∣β^j∣∉(0,aλ)|\hat\beta_j| \notin (0, a\lambda)∣β^​j​∣∈/(0,aλ) almost surely.
  2. Lemma EC.1: the empirical risk is (2σL+Cμ)(2\sigma_L + \mathcal C_\mu)(2σL​+Cμ​)-Lipschitz on the box with high probability.
  3. Proposition 3: uniform deviation of Ln\mathcal L_nLn​ from L\mathbb LL over {∥β∥∞≤R,∥β∥0≤p′}\{\|\beta\|_\infty \le R, \|\beta\|_0 \le p'\}{∥β∥∞​≤R,∥β∥0​≤p′}.
  4. Proposition 4: ∥β^∥0≤pu′−1\|\hat\beta\|_0 \le p'_u - 1∥β^​∥0​≤pu′​−1 with high probability.
  5. Lemma EC.2: comparison of the Lasso solution with βεA∗\beta^*_{\varepsilon_A}βεA​∗​ in Ln,λ\mathcal L_{n,\lambda}Ln,λ​.
  6. Proposition 5: the joint sparsity and excess-risk events for general ϱ∈(0,1/2)\varrho \in (0, 1/2)ϱ∈(0,1/2).
  7. Proposition 1: the excess-risk bounds (16), (18) at S³ONC solutions for general ϱ\varrhoϱ.

Significance

The theorem shows that second-order stationarity, which first- and second-order methods can certify (the paper's Theorem 2 gives a pseudo-polynomial algorithm), suffices for poly-logarithmic sample complexity in ppp without convexity or RSC. The paper builds on it for nonsmooth losses through smoothing (Theorem 3) and for regularized neural networks (Theorem 4). The same definitions layer (MCP, S³ONC, A-sparsity) serves those results.

The result is proved on paper, in the electronic companion of the cited preprint. Nothing of it is formalized: the platform has no folded concave penalty, no S³ONC and no excess-risk bound for sparse M-estimation without RSC. This mission provides the definitions, the goal and the proof chain as stated by the authors, with two disclosed adjustments (see Formalization scope).

Difficulty

The obvious argument bounds Ln(β^)−L(β^)\mathcal L_n(\hat\beta) - \mathbb L(\hat\beta)Ln​(β^​)−L(β^​) uniformly over the box ∥β∥∞≤R\|\beta\|_\infty \le R∥β∥∞​≤R and then compares β^\hat\betaβ^​ with βεA∗\beta^*_{\varepsilon_A}βεA​∗​. It fails: a covering of a ppp-dimensional box costs a factor ppp, not ln⁡p\ln plnp, in the sample size. The usual repair, RSC, which localizes the estimator near a sparse target, is exactly what the paper does without. β^\hat\betaβ^​ is moreover only a stationary point of a nonconvex objective, not a minimizer, so no optimality inequality over the whole space is available. The probabilistic part requires keeping the constants consistent across several union bounds and two Bernstein inequalities, with failure probabilities that must stay summable in the sparsity level. In Lean, an additional obstacle is that suprema over uncountable sparse sets are not obviously measurable.

Formalization scope

  • Data: an abstract measurable space W\mathcal WW (its embedding in Rq\mathbb R^qRq plays no role), independent ZiZ_iZi​ with common law μ\muμ. L(β,⋅)L(\beta, \cdot)L(β,⋅) is measurable and μ\muμ-integrable for every β\betaβ, and L\mathbb LL is bounded below, so inf⁡βL(β)\inf_\beta \mathbb L(\beta)infβ​L(β) is a genuine infimum.
  • Norms: the Euclidean norm is written out (Mathlib's norm on Fin p → ℝ is the sup norm). ∥⋅∥ψ1\|\cdot\|_{\psi_1}∥⋅∥ψ1​​ is the published Orlicz norm HighDimProb.Concentration.subexponentialNorm, always together with an explicit witness of sub-exponentiality. The paper cites the equivalent moment form; the difference is absorbed by the universal constants.
  • Bernstein constant: (12) and the analogous bound for C(Zi)\mathcal C(Z_i)C(Zi​) used in Lemma EC.1 are hypotheses with their constant ccc, quantified first. Every universal constant (C1C_1C1​–C4C_4C4​, c~\tilde cc~) comes after ccc and before every problem object: ppp, nnn, the distribution, LLL, β^\hat\betaβ^​, Γ\GammaΓ. Remark 1 asserts that such a c∈(0,1/2]c \in (0, 1/2]c∈(0,1/2] exists; the platform's proved bernstein_weighted supplies one.
  • Derivatives: the gradient enters through coordinate partial derivatives, which is all (11), (13), (14) use. Pλ′,Pλ′′P'_\lambda, P''_\lambdaPλ′​,Pλ′′​ are derivatives of the literal integral (4).
  • Probabilities: "with probability at least 1−δ1-\delta1−δ" is an upper bound δ\deltaδ on the outer measure of the failure set.
  • Random vectors: β^\hat\betaβ^​ and β^ℓ1\hat\beta^{\ell_1}β^​ℓ1​ are arbitrary measurable maps with the stated almost-sure properties; no statement constructs them.
  • Corrections: a<1a < 1a<1 is added to Theorem 1 and Proposition 1. It is Proposition 5's hypothesis, which their printed proofs invoke. Proposition 4's ζ1(ϵ)\zeta_1(\epsilon)ζ1​(ϵ) prints σC\sigma_CσC​, and σL\sigma_LσL​ is meant. Theorem 1's λ\lambdaλ is kept as printed (ln⁡(n2/3p)\ln(n^{2/3}p)ln(n2/3p)), although Proposition 1 at ϱ=1/3\varrho = 1/3ϱ=1/3 uses ln⁡(n1/3p)\ln(n^{1/3}p)ln(n1/3p).

The trivializing formalizations are ruled out explicitly: constants chosen after the instance, junk values of non-integrable expectations, empty infima or undefined derivatives, the sup norm in place of the Euclidean norm, and an estimator chosen by the theorem.

Welcome contributions: proofs of the milestones in order; a Lean proof that Assumption 3 implies (12), via the published Bernstein inequality; a measurable-selection or outer-measure lemma for suprema over sparse boxes, which is reusable across high-dimensional statistics.

Selected references

  • H. Liu, Y. Ye, H. Y. Lee, High-dimensional learning under approximate sparsity with applications to nonsmooth estimation and regularized neural networks, Operations Research, 2022; preprint arXiv:1903.00616v2, 2021. https://arxiv.org/abs/1903.00616
  • C.-H. Zhang, Nearly unbiased variable selection under minimax concave penalty, Annals of Statistics 38(2), 2010. https://arxiv.org/abs/1002.4734
  • J. Fan, R. Li, Variable selection via nonconcave penalized likelihood and its oracle properties, Journal of the American Statistical Association 96, 2001. https://doi.org/10.1198/016214501753382273
  • S. N. Negahban, P. Ravikumar, M. J. Wainwright, B. Yu, A unified framework for high-dimensional analysis of M-estimators with decomposable regularizers, Statistical Science 27(4), 2012. https://arxiv.org/abs/1010.2731
  • P.-L. Loh, M. J. Wainwright, Regularized M-estimators with nonconvexity: statistical and algorithmic theory for local optima, Journal of Machine Learning Research 16, 2015. https://arxiv.org/abs/1305.2436
  • R. Vershynin, Introduction to the non-asymptotic analysis of random matrices, in Compressed Sensing: Theory and Applications, Cambridge University Press, 2012. https://arxiv.org/abs/1011.3027
11 thms1 active userReviewed
Algorithmic Game TheoryControl TheoryProbability·Captain: mikedeng1

Terminal Ranking Games: The Rank-Based Mean Field Tournament Has an Equilibrium, Characterized by an Explicit Quantile Formula, a Fixed-Point Equation for the Mean and an Explicit Game ValueResearch Paper

Motivation

Tournaments and contests reward agents by their relative standing: sales bonuses for the top performers, promotions, prizes for the first to finish, research competitions. Since Lazear and Rosen (Rank-order tournaments as optimum labor contracts, 1981) such rank-order incentives have been a standard object in economics and operations research, and the design question of which reward schedule elicits which behaviour is central to the area. With a large population, the strategic interaction becomes a mean field game: each agent responds to the distribution of the others' outcomes rather than to individual opponents.

Bayraktar and Zhang (Terminal Ranking Games, arXiv:1906.09628v2, 2020; Mathematics of Operations Research 2021) study such a game in continuous time. Each player steers a Brownian project value by costly effort and is paid at a fixed terminal time according to her own value, her rank in the population, and the population mean. Their main result solves the equilibrium semi-explicitly. Related earlier work treats rank-based rewards by completion time (Bayraktar, Cvitanić and Zhang, Large tournament games, 2019) and by terminal rank in a strong formulation (Bayraktar and Zhang, A rank-based mean field game in the strong formulation, 2016).

Setting

Fix a horizon T>0T>0T>0, a cost coefficient c>0c>0c>0, a volatility σ>0\sigma>0σ>0 and an initial value x0∈Rx_0\in\mathbb Rx0​∈R. On a probability space (Ω,P)(\Omega,P)(Ω,P) let BBB be a real Brownian motion, and let XT=x0+σBTX_T=x_0+\sigma B_TXT​=x0​+σBT​ be the terminal project value under zero effort.

A reward function R(x,r,m)R(x,r,m)R(x,r,m) depends on the player's terminal value xxx, her rank r∈[0,1]r\in[0,1]r∈[0,1] and the population mean mmm; it is weakly increasing in each argument. The class Rb\mathcal R_bRb​ collects the bounded ones. For a population law μ\muμ on R\mathbb RR with c.d.f. FμF_\muFμ​ and mean mμm_\mumμ​, write Rμ(x)=R(x,Fμ(x),mμ)R_\mu(x)=R(x,F_\mu(x),m_\mu)Rμ​(x)=R(x,Fμ​(x),mμ​): the payment received at terminal value xxx when the others are distributed as μ\muμ.

Effort changes the law of the path. In the weak formulation used by the paper, a control is a probability measure QQQ equivalent to PPP, and the quadratic effort cost becomes the relative entropy H(Q∣P)H(Q|P)H(Q∣P). Given the population law μ~\tilde\muμ~​, the single player's value is

V(R,μ~)=sup⁡Q∼P EQ[Rμ~(XT)]−2cσ2H(Q ∣ P).(2.3)V(R,\tilde\mu)=\sup_{Q\sim P}\ E^Q\big[R_{\tilde\mu}(X_T)\big]-2c\sigma^2H(Q\,|\,P). \tag{2.3}V(R,μ~​)=Q∼Psup​ EQ[Rμ~​​(XT​)]−2cσ2H(Q∣P).(2.3)

A law μ\muμ is an equilibrium if it is a fixed point of the best response: some optimal QQQ for V(R,μ)V(R,\mu)V(R,μ) gives XTX_TXT​ the law μ\muμ.

The goal concerns the subclass Rbrm\mathcal R^{rm}_bRbrm​ of bounded rewards R(r,m)R(r,m)R(r,m) that do not depend on xxx and are continuous in mmm. Let NNN be the standard normal c.d.f., N−1N^{-1}N−1 its quantile function, qμ(r)=inf⁡{x:r≤Fμ(x)}q_\mu(r)=\inf\{x:r\le F_\mu(x)\}qμ​(r)=inf{x:r≤Fμ​(x)} the quantile function of μ\muμ, and

ym(r)=∫0re−R(z,m)/2cσ2dz∫01e−R(z,m)/2cσ2dz,g(m)=x0+σT∫01N−1(ym(r)) dr.y_m(r)=\frac{\int_0^r e^{-R(z,m)/2c\sigma^2}dz}{\int_0^1 e^{-R(z,m)/2c\sigma^2}dz},\qquad g(m)=x_0+\sigma\sqrt T\int_0^1N^{-1}(y_m(r))\,dr .ym​(r)=∫01​e−R(z,m)/2cσ2dz∫0r​e−R(z,m)/2cσ2dz​,g(m)=x0​+σT​∫01​N−1(ym​(r))dr.

Formalization targets

Goal: Theorem 3.2 (pp. 7–8)

For R∈RbrmR\in\mathcal R^{rm}_bR∈Rbrm​:

  1. an equilibrium exists;
  2. μ\muμ is an equilibrium if and only if it has a finite mean mμm_\mumμ​ and
qμ(r)=x0+σT N−1(ymμ(r))(0<r<1),mμ=g(mμ);(3.2–3.3)q_\mu(r)=x_0+\sigma\sqrt T\,N^{-1}\big(y_{m_\mu}(r)\big)\quad(0<r<1),\qquad m_\mu=g(m_\mu); \tag{3.2–3.3}qμ​(r)=x0​+σT​N−1(ymμ​​(r))(0<r<1),mμ​=g(mμ​);(3.2–3.3)
  1. for every equilibrium, V(R,μ)=2cσ2ln⁡β(μ)=−2cσ2ln⁡∫01e−R(z,mμ)/2cσ2dzV(R,\mu)=2c\sigma^2\ln\beta(\mu)=-2c\sigma^2\ln\int_0^1e^{-R(z,m_\mu)/2c\sigma^2}dzV(R,μ)=2cσ2lnβ(μ)=−2cσ2ln∫01​e−R(z,mμ​)/2cσ2dz, where β(μ)=∫f0(y)eRμ(y)/2cσ2dy\beta(\mu)=\int f_0(y)e^{R_\mu(y)/2c\sigma^2}dyβ(μ)=∫f0​(y)eRμ​(y)/2cσ2dy and f0f_0f0​ is the N(x0,σ2T)\mathcal N(x_0,\sigma^2T)N(x0​,σ2T) density.

No uniqueness is claimed.

Milestones

  • (2.6), p. 5: V(R,μ~)=sup⁡μ∼PT∫Rμ~ dμ−2cσ2H(μ∣N(x0,σ2T))V(R,\tilde\mu)=\sup_{\mu\sim P_T}\int R_{\tilde\mu}\,d\mu-2c\sigma^2H(\mu|\mathcal N(x_0,\sigma^2T))V(R,μ~​)=supμ∼PT​​∫Rμ~​​dμ−2cσ2H(μ∣N(x0​,σ2T)), for R∈RbR\in\mathcal R_bR∈Rb​.
  • Proposition 2.1, p. 5: the best response exists, its terminal law has density f0eRμ~/2cσ2/β(μ~)f_0e^{R_{\tilde\mu}/2c\sigma^2}/\beta(\tilde\mu)f0​eRμ~​​/2cσ2/β(μ~​), and V(R,μ~)=2cσ2ln⁡β(μ~)V(R,\tilde\mu)=2c\sigma^2\ln\beta(\tilde\mu)V(R,μ~​)=2cσ2lnβ(μ~​), for R∈RbR\in\mathcal R_bR∈Rb​.
  • Theorem 3.1, p. 7: μ\muμ is an equilibrium iff it has a strictly positive density fμ=f0eRμ/2cσ2/β(μ)f_\mu=f_0e^{R_\mu/2c\sigma^2}/\beta(\mu)fμ​=f0​eRμ​/2cσ2/β(μ), for R∈RbR\in\mathcal R_bR∈Rb​.
  • Proof of Theorem 3.2, p. 8: ∣(g(m)−x0)/σT∣≤C∫01∣N−1∣=C2/π|(g(m)-x_0)/\sigma\sqrt T|\le C\int_0^1|N^{-1}|=C\sqrt{2/\pi}∣(g(m)−x0​)/σT​∣≤C∫01​∣N−1∣=C2/π​ with C=exp⁡(∥R(1,⋅)−R(0,⋅)∥∞/2cσ2)C=\exp(\|R(1,\cdot)-R(0,\cdot)\|_\infty/2c\sigma^2)C=exp(∥R(1,⋅)−R(0,⋅)∥∞​/2cσ2).
  • Proof of Theorem 3.2, p. 8: ggg is continuous on the compact interval containing its range.

Significance

The theorem reduces an infinite-dimensional fixed point, over laws on R\mathbb RR defined through a control problem on path space, to a scalar equation for the mean. Everything else is explicit: the equilibrium law is a reparametrized Gaussian quantile, and the game value is a closed form in RRR. The paper's later results build on this: the comparison of game values under the Lorenz order of rewards (Theorem 4.1), the characterization of rewards that realize a target equilibrium (Theorem 5.1), and the tournament design problems of Section 5 all start from (3.2) and the value formula.

The result is proved in the paper, partly by appeal to the literature on Schrödinger bridges; Proposition 2.1 is stated there without proof. None of it is formalized. A formal development would supply the first machine-checked mean field equilibrium of a rank-based game, the entropic weak formulation of a control problem with a terminal reward, and a verified explicit solution against which numerical schemes can be checked.

Difficulty

The reduction from path measures to terminal laws, (2.6), needs the disintegration of QQQ along XTX_TXT​ (the Schrödinger bridge) and the chain rule for relative entropy; only one inequality follows from data processing. The best response is a Gibbs variational principle on the line, but the optimizer must be lifted back to path space and every optimizer must be shown to have the same terminal law. In Theorem 3.2 the characterization requires inverting y(r)=N((qμ(r)−x0)/σT)y(r)=N((q_\mu(r)-x_0)/\sigma\sqrt T)y(r)=N((qμ​(r)−x0​)/σT​), which in turn requires differentiating through a quantile function when RRR is only monotone in rrr, not continuous. Existence needs integrability of N−1N^{-1}N−1, which is unbounded at both ends, uniformly in mmm, and continuity of ggg by dominated convergence. The natural shortcut, treating the equilibrium as a density solving (3.1), does not prove the theorem: the equilibrium is defined through the control problem, and connecting the two is the content of the milestones.

Formalization scope

All declarations live in the namespace TerminalRank.Equilibrium, in one definitions module Model. Conventions:

  • Ω\OmegaΩ is an arbitrary measurable space with a probability measure PPP under which B:R≥0→Ω→RB:\mathbb R_{\ge0}\to\Omega\to\mathbb RB:R≥0​→Ω→R satisfies Mathlib's IsBrownianReal. This is the paper's Wiener space up to relabelling, and also covers its Remark 2.1 (larger filtrations). TTT has type ℝ≥0, and σ>0\sigma>0σ>0 (the paper needs only σ≠0\sigma\ne0σ=0).
  • Rewards are real-valued, and the bounded reward classes carry a uniform bound; monotonicity and boundedness are required for ranks r∈[0,1]r\in[0,1]r∈[0,1] only. Three milestones, stated in the paper for general R∈RR\in\mathcal RR∈R, are specialized to R∈RbR\in\mathcal R_bR∈Rb​, where the reward expectation in (2.3) is defined; the goal assumes R∈Rbrm⊂RbR\in\mathcal R^{rm}_b\subset\mathcal R_bR∈Rbrm​⊂Rb​ anyway. The population law has a finite first moment wherever the paper uses RμR_\muRμ​; equilibrium includes this condition.
  • Relative entropy is Mathlib's klDiv, valued in [0,∞][0,\infty][0,∞]. The suprema in (2.3) and (2.6) run over measures with finite entropy; the excluded ones have value −∞-\infty−∞ in the paper, so nothing changes.
  • The quantile is the left-continuous inverse inf⁡{x:r≤F(x)}\inf\{x:r\le F(x)\}inf{x:r≤F(x)}, and (3.2) is required for r∈(0,1)r\in(0,1)r∈(0,1). The goal states the finiteness of the mean of μ\muμ explicitly; it holds for every equilibrium.

VVV, optimality and equilibrium are defined from the path-space problem (2.3). A formalization that defines them by (2.6), (2.9) or (3.1), or replaces (Ω,P,B)(\Omega,P,B)(Ω,P,B) by a single Gaussian variable, would make the milestones definitional and is ruled out.

Needed infrastructure: Gibbs variational principle (published on the platform as DonskerVaradhan.integral_sub_klDiv_le_log_integral_exp and DonskerVaradhan.klDiv_tilted_self_eq), disintegration and the chain rule for klDiv, Brownian bridges, change of variables for quantile functions, and E∣Z∣=2/πE|Z|=\sqrt{2/\pi}E∣Z∣=2/π​. The quantile and Brownian-bridge lemmas are reusable well beyond this mission. Contributions toward any milestone, and auxiliary lemmas on these tools, are welcome.

Selected references

  • E. Bayraktar and Y. Zhang, Terminal Ranking Games, arXiv:1906.09628v2, 2020; Mathematics of Operations Research, 2021. https://arxiv.org/abs/1906.09628
  • E. Bayraktar, J. Cvitanić and Y. Zhang, Large tournament games, Annals of Applied Probability 29(6), 2019. https://doi.org/10.1214/19-AAP1490
  • E. Bayraktar and Y. Zhang, A rank-based mean field game in the strong formulation, Electronic Communications in Probability 21, 2016. https://doi.org/10.1214/16-ECP24
  • E. P. Lazear and S. Rosen, Rank-order tournaments as optimum labor contracts, Journal of Political Economy 89(5), 1981. https://doi.org/10.1086/261010
  • H. Föllmer, Random fields and diffusion processes, École d'Été de Probabilités de Saint-Flour XV–XVII, Lecture Notes in Mathematics 1362, Springer, 1988. https://doi.org/10.1007/BFb0086180
  • Y. Chen, T. T. Georgiou and M. Pavon, On the relation between optimal transport and Schrödinger bridges: a stochastic control viewpoint, Journal of Optimization Theory and Applications 169, 2016. https://doi.org/10.1007/s10957-015-0803-z
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Bandit AlgorithmsMachine LearningProbability·Captain: mikedeng1

Online Learning over a Finite Action Set with Limited Switching: An Algorithm for Prediction From Experts Whose Regret and Number of Switches Are Both O(√(T log n log(1/δ))) with Probability 1 − δResearch Paper

Motivation

In prediction from experts (PFE), an online learner chooses one of nnn actions in each of TTT rounds, and an adversary assigns each action a loss in [0,1][0,1][0,1]. Performance is measured by regret, the learner's total loss minus that of the best single action in hindsight. In many applications changing the action is itself costly: re-routing traffic, re-balancing a portfolio, re-deploying a model. The number of switches, rounds in which the action changes, is then a second resource to keep small.

It has long been known that both quantities can be kept at O(Tlog⁡n)O(\sqrt{T\log n})O(Tlogn​) in expectation. Kalai and Vempala's multiplicative Follow the Perturbed Leader (Kalai–Vempala 2005) and Devroye, Lugosi and Neu's random-walk perturbation (Devroye et al. 2015) both achieve this. Devroye et al. asked for guarantees that hold with high probability. A bound in expectation says little about a single run: the switch count of these algorithms can have heavy upper tails. Altschuler and Talwar (arXiv:1803.01548, COLT 2018; Mathematics of Operations Research 2021) gave the first algorithms whose regret and switches are both O(Tlog⁡nlog⁡(1/δ))O(\sqrt{T\log n\log(1/\delta)})O(Tlognlog(1/δ)​) with probability 1−δ1-\delta1−δ. They used this to characterise the optimal regret under a hard switching budget, both for PFE and for multi-armed bandits.

Setting

A loss sequence is (ℓt)t≥1(\ell_t)_{t\ge1}(ℓt​)t≥1​ with ℓt:[n]→[0,1]\ell_t:[n]\to[0,1]ℓt​:[n]→[0,1]. The adversary is oblivious: it fixes the whole sequence before the game, independently of the learner's randomness. A randomized online algorithm A\mathcal AA draws internal randomness ω\omegaω from a probability space (Ω,μ)(\Omega,\mu)(Ω,μ). At round ttt it plays an action it∈[n]i_t\in[n]it​∈[n] that is a function of ω\omegaω and of the past losses ℓ1,…,ℓt−1\ell_1,\dots,\ell_{t-1}ℓ1​,…,ℓt−1​ only. This is full-information feedback: after round ttt the whole vector ℓt\ell_tℓt​ is revealed. Then

RegretT=∑t=1Tℓt(it)−min⁡i∈[n]∑t=1Tℓt(i),SwitchesT=#{t∈{2,…,T}:it≠it−1}.\mathrm{Regret}_T=\sum_{t=1}^T\ell_t(i_t)-\min_{i\in[n]}\sum_{t=1}^T\ell_t(i),\qquad \mathrm{Switches}_T=\#\{t\in\{2,\dots,T\}:i_t\ne i_{t-1}\}.RegretT​=t=1∑T​ℓt​(it​)−i∈[n]min​t=1∑T​ℓt​(i),SwitchesT​=#{t∈{2,…,T}:it​=it−1​}.

Follow the Perturbed Leader (FPL) with perturbations Pt(i)P_t(i)Pt​(i) plays at round ttt the minimiser of ∑s=0t−1(ℓs(i)+Ps+1(i))\sum_{s=0}^{t-1}(\ell_s(i)+P_{s+1}(i))∑s=0t−1​(ℓs​(i)+Ps+1​(i)), with ℓ0:=0\ell_0:=0ℓ0​:=0. FPLε∗^*_\varepsilonε∗​ perturbs only once, with P1(i)=−R(i)/εP_1(i)=-R(i)/\varepsilonP1​(i)=−R(i)/ε, where R(1),…,R(n)R(1),\dots,R(n)R(1),…,R(n) are i.i.d. standard exponential.

Framework 1 turns an algorithm A\mathcal AA into a batched algorithm B\mathcal BB. B\mathcal BB runs a copy of A\mathcal AA with fresh randomness. The copy sees only the losses since its epoch began. The epoch ends just before the copy would exceed S′S'S′ switches, and a new copy starts there. EEE is the number of epochs used in TTT rounds. BFPLδ∗^*_\deltaδ∗​ is Framework 1 applied to FPLε∗^*_\varepsilonε∗​ with

N=⌈log⁡(2/δ)⌉,ε=12Nlog⁡n/T,S′=135Tlog⁡n/N.N=\lceil\log(2/\delta)\rceil,\qquad \varepsilon=\tfrac12\sqrt{N\log n/T},\qquad S'=135\sqrt{T\log n/N}.N=⌈log(2/δ)⌉,ε=21​Nlogn/T​,S′=135Tlogn/N​.

Formalization targets

Goal: Theorem 1 (p. 8)

There is an absolute constant C>0C>0C>0 such that for all T,n≥1T,n\ge1T,n≥1 and δ∈(0,12)\delta\in(0,\tfrac12)δ∈(0,21​) some randomized online algorithm A\mathcal AA satisfies, for every oblivious loss sequence,

P(RegretT(A)≤CTlog⁡nlog⁡(1/δ) ∧ SwitchesT(A)≤CTlog⁡nlog⁡(1/δ))≥1−δ.\mathbb P\Big(\mathrm{Regret}_T(\mathcal A)\le C\sqrt{T\log n\log(1/\delta)}\ \wedge\ \mathrm{Switches}_T(\mathcal A)\le C\sqrt{T\log n\log(1/\delta)}\Big)\ge1-\delta.P(RegretT​(A)≤CTlognlog(1/δ)​ ∧ SwitchesT​(A)≤CTlognlog(1/δ)​)≥1−δ.

The algorithm may depend on TTT, nnn and δ\deltaδ, as on the page, but not on the losses. The constant is left unspecified, so a sharper constant would not change the goal.

Milestones

  1. Lemma 7 (p. 13): E[Switchesτ(FPLε∗)]≤(ετ+2log⁡n)/(1−ε)\mathbb E[\mathrm{Switches}_\tau(\mathrm{FPL}^*_\varepsilon)]\le(\varepsilon\tau+2\log n)/(1-\varepsilon)E[Switchesτ​(FPLε∗​)]≤(ετ+2logn)/(1−ε).
  2. Lemma 3 (p. 10): if E[Switchesτ0(A)]≤cAτ0\mathbb E[\mathrm{Switches}_{\tau_0}(\mathcal A)]\le c_{\mathcal A}\sqrt{\tau_0}E[Switchesτ0​​(A)]≤cA​τ0​​ with τ0=min⁡(T,⌈8T/N⌉)\tau_0=\min(T,\lceil8T/N\rceil)τ0​=min(T,⌈8T/N⌉), then Framework 1 with S′=23cAT/NS'=23c_{\mathcal A}\sqrt{T/N}S′=23cA​T/N​ has P(E>N)≤e−N\mathbb P(E>N)\le e^{-N}P(E>N)≤e−N and P(SwitchesT>N(S′+1))≤e−N\mathbb P(\mathrm{Switches}_T>N(S'+1))\le e^{-N}P(SwitchesT​>N(S′+1))≤e−N.
  3. Lemma 17 (p. 27), Be-The-Leader: ∑t=0Tℓt(it+1)≤∑t=0Tℓt(i)\sum_{t=0}^T\ell_t(i_{t+1})\le\sum_{t=0}^T\ell_t(i)∑t=0T​ℓt​(it+1​)≤∑t=0T​ℓt​(i).
  4. Lemma 5 (p. 13): RegretT(FPL)≤M(SwitchesT+1)+max⁡i∑t=1T+1Pt(i)−∑t=1T+1Pt(it)\mathrm{Regret}_T(\mathrm{FPL})\le M(\mathrm{Switches}_T+1)+\max_i\sum_{t=1}^{T+1}P_t(i)-\sum_{t=1}^{T+1}P_t(i_t)RegretT​(FPL)≤M(SwitchesT​+1)+maxi​∑t=1T+1​Pt​(i)−∑t=1T+1​Pt​(it​).
  5. Corollary 6 for BFPL∗^*∗ (p. 14): RegretT≤SwitchesT+E+∑e<Emax⁡iRe(i)/ε\mathrm{Regret}_T\le\mathrm{Switches}_T+E+\sum_{e<E}\max_iR_e(i)/\varepsilonRegretT​≤SwitchesT​+E+∑e<E​maxi​Re​(i)/ε.
  6. Lemma 18 (p. 28): E[etX]≤nt/(1−t)\mathbb E[e^{tX}]\le n^t/(1-t)E[etX]≤nt/(1−t) for the maximum XXX of nnn standard exponentials.
  7. Lemma 9 (p. 14): P(∑e=1Nmax⁡iRe(i)>6Nlog⁡n)≤e−N\mathbb P(\sum_{e=1}^N\max_iR_e(i)>6N\log n)\le e^{-N}P(∑e=1N​maxi​Re​(i)>6Nlogn)≤e−N for N,n≥2N,n\ge2N,n≥2.
  8. Theorem 8 (p. 13): BFPLδ∗^*_\deltaδ∗​ itself satisfies the bound of Theorem 1 for n≥2n\ge2n≥2.

Significance

The result separates two notions of "optimal". Expected-value bounds on switching do not control a single run, and the paper shows (Appendix B) that naive restarting does not concentrate. Theorem 1 is the black box behind the paper's later results: the Θ~\tilde\ThetaΘ~ characterisation of minimax regret under a switching budget SSS, with a phase transition at S≈Tlog⁡nS\approx\sqrt{T\log n}S≈Tlogn​, and the switching-cost corollary obtained by mini-batching. Framework 1 is generic: any algorithm with an expected switching bound of order τ\sqrt\tauτ​ gains a high-probability one.

The paper result is proved, but none of it has been machine-checked. A formalization yields a verified online-learning protocol with oblivious adversaries, a restart framework with fresh randomness, and verified tail bounds for maxima of exponentials. Formalizing it also repairs four printed slips, listed under Formalization scope.

Difficulty

The obvious approach runs A\mathcal AA about log⁡(1/δ)\log(1/\delta)log(1/δ) times in fixed-length blocks and applies Markov's inequality in each. It fails: a single block can use far too many switches with probability that is not small enough. Framework 1 therefore uses epochs of random length, ended by the switch budget. The epoch lengths are then dependent, and the final epoch is truncated at TTT. The concentration argument has to handle both. On the regret side, Lemma 5 is pointwise, but summing it over random epochs and then controlling the sum of perturbation maxima needs a sub-exponential tail bound for maxima of exponentials.

Formalization scope

Rounds are 1-based, and losses are ℓ:N→Fin n→R\ell:\mathbb N\to\mathrm{Fin}\,n\to\mathbb Rℓ:N→Finn→R with values in [0,1][0,1][0,1]. An online algorithm has type Ω→(t:N)→(Fin(t−1)→Fin n→R)→Fin n\Omega\to(t:\mathbb N)\to(\mathrm{Fin}(t-1)\to\mathrm{Fin}\,n\to\mathbb R)\to\mathrm{Fin}\,nΩ→(t:N)→(Fin(t−1)→Finn→R)→Finn: at round ttt it sees only ω\omegaω and ℓ1,…,ℓt−1\ell_1,\dots,\ell_{t-1}ℓ1​,…,ℓt−1​. The adversary is a deterministic loss sequence, quantified after the algorithm, which is the page's own reduction (p. 5). High-probability statements bound the outer measure of the failure event by δ\deltaδ. Expectations are lower Lebesgue integrals of natural-valued switch counts. The O(⋅)O(\cdot)O(⋅) of Theorems 1 and 8 is an absolute constant C>0C>0C>0 chosen before TTT, nnn and δ\deltaδ. Argmins break ties towards the lowest index. Framework 1 takes randomness ω:N→Ω\omega:\mathbb N\to\Omegaω:N→Ω under the infinite product measure, one coordinate per epoch.

Three formalizations of the goal would be trivial, and all are excluded. An algorithm that could see ℓt\ell_tℓt​ or the future would simply play the best action in hindsight. A constant CCC chosen after TTT could be C=TC=TC=T. A loss sequence chosen before the algorithm would let the algorithm depend on it.

The printed slips and how they are handled:

  • FPL* sign. The paper perturbs by +R/ε+R/\varepsilon+R/ε. With one-sided exponentials that variant violates Lemma 7, so the perturbation is −R/ε-R/\varepsilon−R/ε.
  • Lemma 5 and Corollary 6. These need M(SwitchesT+1)M(\mathrm{Switches}_T+1)M(SwitchesT​+1) and +E+E+E; the printed forms fail at T=1T=1T=1.
  • Lemma 3. It takes an integer N≥2N\ge2N≥2 with δ/2=e−N\delta/2=e^{-N}δ/2=e−N, it assumes the switching hypothesis only at the horizon the proof uses, and it counts one boundary switch per epoch.
  • BFPLδ∗^*_\deltaδ∗​. It uses N=⌈log⁡(2/δ)⌉N=\lceil\log(2/\delta)\rceilN=⌈log(2/δ)⌉.
  • Measurability. Lemma 3 assumes that A\mathcal AA's actions are measurable in ω\omegaω.

The development needs:

  • product and infinite-product measures of exponential laws (in Mathlib);
  • Markov's inequality and Azuma–Hoeffding for submartingales with bounded differences;
  • the memoryless property of the exponential law;
  • Chernoff bounds.

The online-learning layer (protocol, regret, switches, FPL, the restart framework) is reusable for other switching-cost results in the paper and elsewhere. Proofs of any milestone are welcome, as are alternative routes to Theorem 1, such as the random-walk perturbation of §2.5.

Selected references

  • J. M. Altschuler and K. Talwar, Online learning over a finite action set with limited switching, COLT 2018; Mathematics of Operations Research 46(1), 2021. arXiv:1803.01548v2
  • A. Kalai and S. Vempala, Efficient algorithms for online decision problems, Journal of Computer and System Sciences 71(3), 2005. doi:10.1016/j.jcss.2004.10.016
  • L. Devroye, G. Lugosi and G. Neu, Random-walk perturbations for online combinatorial optimization, IEEE Transactions on Information Theory 61(7):4099–4106, 2015. doi:10.1109/TIT.2015.2428253
  • N. Cesa-Bianchi and G. Lugosi, Prediction, Learning, and Games, Cambridge University Press, 2006. doi:10.1017/CBO9780511546921
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Combinatorics·Captain: @bwdaugherty

Zero-Core Theorem for Ramsey R(5,5)Research Paper

Motivation

The Zero-Core Theorem establishes a fundamental structural property of Ramsey graph colorings: the obstruction preventing extension of the champion R(5,5) coloring from n=43 to n=44 is fully distributed across all constraints, with no individual bottleneck.

This is the first formalization of an essential core theorem in Ramsey theory.

Setting

Given an infeasible constraint system S = {c₁, ..., cₘ}, a constraint cᵢ is essential if S \ {cᵢ} is feasible. The essential core 𝓔 ⊆ S is the set of all essential constraints.

Formalization target

Goal: Prove that the essential core of the K₄₄ extension problem is empty (𝓔 = ∅).

The champion K₄₃ coloring (with 137 monochromatic K₅ violations) contains 2,480 monochromatic K₄ subgraphs. The theorem proves that removing any single K₄ constraint from this system leaves it infeasible.

Significance

This demonstrates that R(5,5) = 43 is a "deep" combinatorial fact arising from holistic constraint interaction, not from any individual forcing constraint. The distributed nature of the obstruction connects to permutation-invariant energy barriers in optimization landscapes.

Difficulty

The theorem requires:

  1. Defining constraint systems and feasibility
  2. Formalizing the essential core concept
  3. Proving infeasibility is preserved under single-constraint removal
  4. Computational verification across 2,480 cases

Formalization scope

  • Constraint satisfaction problems
  • Graph coloring extensions
  • Essential core theory
  • Computational proof certificates

Selected references

  • Daugherty, B. et al. Falsification of R(8,8) > 293: Exhaustive Max-Clique Verification. Zenodo, 2026. DOI: 10.5281/zenodo.19414435
  • Exoo, G. A lower bound for R(5,5). J. Graph Theory, 1989.
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Algorithmic Game TheoryControl TheoryProbability+1·Captain: mikedeng1

Dynamic Set Values for Nonzero-Sum Games with Multiple Equilibriums: The Set Value of a Continuous-Time Nonzero-Sum Stochastic Differential Game Satisfies the Dynamic Programming PrincipleResearch Paper

Motivation

A nonzero-sum game can have several Nash equilibria with different cost vectors. Selecting one equilibrium before asking how the game behaves over time loses information and may make a proposed dynamic rule depend on that selection. Feinstein, Rudloff and Zhang study the entire set of equilibrium cost vectors and ask whether it can be evaluated consistently after the game is stopped. Their continuous-time result is Theorem 3.9 of the pinned preprint, which the authors identify as the main result of the paper. It follows a discrete-time set-value principle developed earlier in the same work. The question is relevant to stochastic games whose controls use the observed path history and whose players need not share an objective.

Setting

Fix a horizon T>0T>0T>0, a positive state dimension ddd, and a positive number NNN of players. The canonical path space is

Ω={ω∈C([0,T];Rd):ω0=0}.\Omega=\{\omega\in C([0,T];\mathbb R^d):\omega_0=0\}.Ω={ω∈C([0,T];Rd):ω0​=0}.

Its coordinate process is Bt(ω)=ωtB_t(\omega)=\omega_tBt​(ω)=ωt​. The measure P0\mathbb P_0P0​ is Wiener measure, and Ft\mathcal F_tFt​ is the filtration generated by the coordinates through time ttt, augmented by Borel P0\mathbb P_0P0​-null events. Each player iii has a nonempty convex action set AiA_iAi​. A control profile α=(α1,…,αN)\alpha=(\alpha^1,\ldots,\alpha^N)α=(α1,…,αN) consists of progressively measurable, AiA_iAi​-valued processes. A unilateral deviation may be any such process for that player.

The drift bbb depends on the entire profile, while player iii's running cost fif_ifi​ depends on that player's own action. The terminal cost vector is ξ\xiξ. Assumption 3.1 requires progressive measurability and boundedness of these data. Assumption 3.6 requires uniform continuity in time and path history, and uniform continuity in actions. For a history (t,ω)(t,\omega)(t,ω), concatenation ω⊗tω~\omega\otimes_t\widetilde\omegaω⊗t​ω holds the old path through ttt and continues with the increment path afterward. The paper changes measure from P0\mathbb P_0P0​ with a Girsanov density MT−tt,ω,αM^{t,\omega,\alpha}_{T-t}MT−tt,ω,α​, then defines the cost Ji(t,ω,α)J_i(t,\omega,\alpha)Ji​(t,ω,α) as the expected shifted terminal cost plus running cost.

An ε\varepsilonε-equilibrium is a profile whose cost for every player is at most ε\varepsilonε above the cost of every unilateral deviation. Let Oε(y)O_\varepsilon(y)Oε​(y) be the open Euclidean ball of radius ε\varepsilonε around yyy. The set value is the intersection of the relaxed value sets

Vε(t,ω)=⋃α∈NEε(t,ω)Oε(J(t,ω,α)),V(t,ω)=⋂ε>0Vε(t,ω).\mathbb V_\varepsilon(t,\omega) =\bigcup_{\alpha\in NE_\varepsilon(t,\omega)} O_\varepsilon(J(t,\omega,\alpha)),\qquad \mathbb V(t,\omega)=\bigcap_{\varepsilon>0}\mathbb V_\varepsilon(t,\omega).Vε​(t,ω)=α∈NEε​(t,ω)⋃​Oε​(J(t,ω,α)),V(t,ω)=ε>0⋂​Vε​(t,ω).

The open lower envelope V^ε\widehat{\mathbb V}_\varepsilonVε​ is the union of Vε′\mathbb V_{\varepsilon'}Vε′​ over 0<ε′<ε0<\varepsilon'<\varepsilon0<ε′<ε. These objects are defined even if the game has no exact equilibrium.

Formalization targets

The target is Theorem 3.9 in the form (3.12) treated in its proof, at the zero history and initial time. For a stopping time τ\tauτ with τ(0)>0\tau(0)>0τ(0)>0, let J(τ,η;0,0,α)J(\tau,\eta;0,0,\alpha)J(τ,η;0,0,α) denote the cost of the game stopped at τ\tauτ with bounded Fτ\mathcal F_\tauFτ​-measurable terminal vector η\etaη. The claim is

V(0,0)=⋂ε>0{y:∃η,αα∈NEε(τ,η;0,0),y∈Oε(J(τ,η;0,0,α)),P0 ⁣(η∉V^ε(τ,B))≤ε}.\mathbb V(0,0)=\bigcap_{\varepsilon>0} \left\{y:\begin{array}{l} \exists\eta,\alpha\quad \alpha\in NE_\varepsilon(\tau,\eta;0,0),\\ y\in O_\varepsilon(J(\tau,\eta;0,0,\alpha)),\\ \mathbb P_0\!\left(\eta\notin \widehat{\mathbb V}_\varepsilon(\tau,B)\right)\le\varepsilon \end{array}\right\}.V(0,0)=ε>0⋂​⎩⎨⎧​y:∃η,αα∈NEε​(τ,η;0,0),y∈Oε​(J(τ,η;0,0,α)),P0​(η∈/Vε​(τ,B))≤ε​⎭⎬⎫​.

The seven milestones reproduce Proposition 3.4, the density moment bound (3.6), the cost-continuity estimate (3.4), Theorem 3.7(i), Theorem 3.8, and both parts of Lemma 3.10. They cover compactness, regularity and measurability of the set value, as well as approximation of stopping data and controls.

Significance

The equality relates the set of full-horizon equilibrium costs to stopped games whose terminal payoff is approximately compatible with the continuation set value. It gives a dynamic characterization without choosing a particular equilibrium. The relaxation by the same ε\varepsilonε in equilibrium, value ball and exceptional-event probability is part of the result; removing one of those terms changes the game being characterized.

The result is proved in the cited preprint. The mission asks for machine-checked proofs of the stated theorem and its supporting results. The reusable development includes canonical finite-horizon Wiener paths, their augmented filtration, path concatenation, progressive control profiles, a coordinatewise stochastic integral interface, and set-valued equilibrium costs. The published Ethier–Kurtz definition of the Itô-integral relation is reused; it supplies a definition, not a proof of this paper's results.

Difficulty

At a stopping time, the continuation value is a set that depends on the observed path. A pointwise description does not by itself show that membership in this random set is measurable at the stopping time. Equilibrium conditions also compare a profile against every progressively measurable unilateral deviation, so their stability cannot be reduced to a comparison of finitely many actions. The Girsanov density introduces another dependency: its stochastic integral and the resulting costs must be genuine integrable random variables before inequalities between cost vectors have their intended meaning.

Formalization scope

Lean represents Rd\mathbb R^dRd and RN\mathbb R^NRN by Euclidean spaces, with Euclidean norms on costs and the action product. Paths are continuous maps on [0,T][0,T][0,T] constrained to start at zero. The canonical process is clamped outside the horizon only to make its notation total. The Wiener law is pinned by Brownian finite-dimensional distributions through TTT and independence of coordinate processes. The filtration adds Borel null sets, so it remains a sub-σ-algebra of the Borel space. Time-indexed controls live on [0,T][0,T][0,T]; the stopping times themselves use WithTop ℝ and are constrained to that interval.

Concatenation uses the second increment strictly after ttt, resolving the overlapping endpoint in the printed indicator formula. Player iii's running cost takes only aia_iai​. The moduli in Assumption 3.6 are common and uniform in the variables specified there. The stopped running cost integrates to τ−t\tau-tτ−t, with an empty interval contributing zero only outside the theorem's admissible range. The goal uses bounded measurable representatives of L∞L^\inftyL∞ terminal payoffs; changing a representative on a null set leaves the expected costs and exceptional probability unchanged.

The statement must retain the full Girsanov density, all progressive deviations, the open envelope V^ε\widehat{\mathbb V}_\varepsilonVε​, and a nonzero player count. A default-zero integral for a nonintegrable payoff, an arbitrary measure in place of Wiener measure, or a restricted deviation class would trivialize or alter it. Solvers can contribute the integrability and stochastic-integral existence facts needed to establish that the definitions have their intended values, followed by proofs of the listed milestones and goal.

Selected references

  • Zachary Feinstein, Birgit Rudloff and Jianfeng Zhang, Dynamic Set Values for Nonzero Sum Games with Multiple Equilibriums, arXiv preprint arXiv:2002.00449v2, 2020, §§3.1–3.3. Preprint.
  • Stewart N. Ethier and Thomas G. Kurtz, Markov Processes: Characterization and Convergence, Wiley, 1986, Chapter 5, §2. Publisher record.
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Control TheoryDynamic ProgrammingProbability+1·Captain: mikedeng1

McKean–Vlasov Optimal Control: Limit Theory and Equivalence Between Different Formulations: The N-Player Common-Noise Control Value Converges to the McKean–Vlasov ValueResearch Paper

Why this limit matters

A controller of a large population may choose a separate action for each participant while all participants experience the same random environment. The resulting optimization problem has a growing state space: with NNN participants, the state records NNN paths and NNN controls. A McKean–Vlasov control problem replaces the empirical distribution of those participants by a conditional distribution given the common noise. Djete, Possamaï and Tan prove that this replacement preserves the optimal value asymptotically, even when the participants have different initial laws and the average of those laws does not converge along the full sequence. Their result is Theorem 3.6(iii) of the 2020 preprint, published in 2022.

The distinction between common and individual noise matters for this claim. Conditional on the common noise, particles can still be correlated through a controller that observes the full particle system. The paper's limit theorem concerns the supremum over all admissible predictable particle controls, rather than one prescribed feedback rule. This is the setting in which a finite population optimization problem can approximate its limiting stochastic control problem. The adjacent Proposition 3.7 describes how the limiting value changes with the initial law.

Setting

Fix a time horizon T>0T>0T>0, state dimension n≥1n\ge1n≥1, individual noise dimension d≥1d\ge1d≥1, and common noise dimension ℓ≥0\ell\ge0ℓ≥0. Let AAA be a nonempty Polish control space with base point a0a_0a0​. A state or noise path belongs to Ck=C([0,T],Rk)C^k=C([0,T],\mathbb R^k)Ck=C([0,T],Rk), with its uniform norm. The coefficients b,σ,σ0b,\sigma,\sigma_0b,σ,σ0​ determine the drift, individual diffusion and common diffusion; LLL and ggg determine running and terminal rewards. The Wasserstein distance Wp\mathcal W_pWp​ measures the discrepancy between probability laws with finite pppth moments.

For an initial law ν\nuν, the strong problem lives on the canonical space Ω=Rn×Cd×Cℓ\Omega=\mathbb R^n\times C^d\times C^\ellΩ=Rn×Cd×Cℓ. Its initial state has law ν\nuν, and W,BW,BW,B are independent Brownian noises relative to the canonical past. An admissible control α\alphaα is predictable and has finite expected integrated pppth power of its distance from a0a_0a0​. The state XαX^\alphaXα solves the controlled equation (2.3). Its coefficients use the conditional law μˉtα\bar\mu_t^\alphaμˉ​tα​ of the stopped state path and current control given the history of BBB; its terminal reward uses the conditional law μTα\mu_T^\alphaμTα​ of the stopped state path. The strong value VS(ν)V_S(\nu)VS​(ν), equation (2.4), is the supremum of expected reward over those controls and their solutions. These definitions appear in Section 2.1.

For N≥1N\ge1N≥1, the particle problem has initial laws ν1,…,νN\nu^1,\ldots,\nu^Nν1,…,νN, separate Brownian noises WiW^iWi, and one shared BBB. Each particle follows equation (2.16) with the empirical state-control law φtN=N−1∑iδ(Xt∧⋅i,αti)\varphi_t^N=N^{-1}\sum_i\delta_{(X^i_{t\wedge\cdot},\alpha_t^i)}φtN​=N−1∑i​δ(Xt∧⋅i​,αti​)​ inside its coefficients. The terminal reward uses the empirical state-path law φtN,X\varphi_t^{N,X}φtN,X​. Equation (2.17) defines VSN(ν1,…,νN)V_S^N(\nu^1,\ldots,\nu^N)VSN​(ν1,…,νN) as the supremum of the average expected reward. The empirical laws are built from the very particles whose equations use them; they are not outside inputs. See Section 2.4.

Formalization targets

The goal is the value comparison in Theorem 3.6(iii), equation (3.3):

lim⁡N→∞∣VSN(ν1,…,νN)−VS ⁣(1N∑i=1Nνi)∣=0.\lim_{N\to\infty}\left|V_S^N(\nu^1,\ldots,\nu^N)-V_S\!\left(\frac1N\sum_{i=1}^N\nu^i\right)\right|=0.N→∞lim​​VSN​(ν1,…,νN)−VS​(N1​i=1∑N​νi)​=0.

The hypotheses include Assumptions 2.1 and 2.12, an embedding A⊂RjA\subset\mathbb R^jA⊂Rj for some j≥1j\ge1j≥1, continuity of LLL and ggg, and a uniform bound on the averages of the initial p′p'p′th moments, where p′>p≥2p'>p\ge2p′>p≥2. The goal does not assume that the averaged initial laws converge. The milestones are the value lower bounds of Propositions 4.15 and 4.16, the subsequence value limit used in equation (4.44), and the initial-law stability statement (3.4) of Proposition 3.7. Each milestone records the particular clause formalized when its printed result contains additional conclusions. Theorem 3.6 and its proof give the source order.

What the result provides

The theorem compares two optimization problems, rather than only the law of a fixed controlled particle system. The comparison permits heterogeneous initial distributions and keeps the common noise in both models. Proposition 3.7 gives a separate stability statement for the limiting value when initial laws converge in Wp\mathcal W_pWp​ with uniformly bounded p′p'p′th moments. Together these statements identify which finite population values are represented by the limiting control formulation. They are proved in the paper; the open task here is a machine checked derivation from faithful statements.

The formal development fixes the interfaces for conditional laws, predictable controls, path dependent coefficients, Brownian Itô integrals, empirical probability laws and extended real rewards. Those interfaces can support later formalizations of common-noise control and propagation of chaos. The present mission does not state Theorem 3.1(i), the approximation clauses of Theorem 3.1(ii)–(iii), Theorem 3.6(ii), or the “In particular” sentence after Proposition 3.7's equation (3.4). Their different conclusions require further canonical and relaxed-control structures, and the last sentence has a topology ambiguity documented in the paper notes.

Main difficulty

The usual fixed-control convergence question is smaller than the target: particle controls may depend on every observed particle and on the common noise, and the target takes a supremum before comparing values. The conditional law in the limiting equation depends on its own solution, while the empirical law in each particle equation depends on the full coupled particle system. Dropping either dependence changes the optimization problem. Uniform p′p'p′th moment control must also coexist with unbounded rewards and the extended real convention for their expectations. The source proof invokes compactness and equivalence between strong, weak and relaxed formulations; formalizing those links is substantial work beyond compiling the goal statement.

Formalization scope

Lean uses EuclideanSpace and continuous maps on [0,T][0,T][0,T] for the path spaces, and Frobenius norms for diffusion matrices. The control type carries a Polish Borel metric and a base point. Pp\mathcal P_pPp​ is a finite-lintegral moment condition, and Wp\mathcal W_pWp​ takes values in R≥0∪{∞}\mathbb R_{\ge0}\cup\{\infty\}R≥0​∪{∞}. Values are extended real suprema over admissible controls and actual solutions. Rewards use the paper's convention ∞−∞=−∞\infty-\infty=-\infty∞−∞=−∞, rather than a default zero integral. Particle counts are positive; Lean player index zero denotes the paper's player one. The case ℓ=0\ell=0ℓ=0 remains included.

Assumption 2.1 includes the displayed Lipschitz, growth and coercive bounds, Borel measurability, nonanticipativity, and lower semicontinuity. Assumption 2.12 factors the coefficients through the state marginal, with σ0\sigma_0σ0​ independent of the control. The paper leaves the topology behind “continuous” unnamed; the formalization uses sequential Wp\mathcal W_pWp​ continuity on finite-moment laws. Its A⊂RjA\subset\mathbb R^jA⊂Rj is read as an isometric embedding. Solutions have continuous paths and are adapted to the completed canonical filtration, while conditional laws use the raw common-noise filtration. The goal states finiteness of both values so its real absolute difference is defined. Equation (4.44) is posed in the subsequence form used by its proof. These choices and the source's printed slips are detailed in the moderation notes.

The interface rules out a free conditional-law flow, a free particle empirical measure, and an uncharacterized Brownian law. The weak and relaxed formulations appear only as context for the paper's proof; this proposal contains the strong and particle layers needed by the four selected milestones. Contributions to the omitted equivalence and compactness results are welcome once their canonical-space definitions have been audited.

Selected references

  • Mao Fabrice Djete, Dylan Possamaï and Xiaolu Tan, McKean–Vlasov optimal control: limit theory and equivalence between different formulations, Mathematics of Operations Research, 2022; arXiv:2001.00925v2. The formal statements use this preprint's pagination and equation numbers.
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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.
1 thm1 active userReviewed
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.
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