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Proposition 3: PPT asymptotic pure-state cost and distillation

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QAlgorithms.Papers.Independent.Intakethird100.P95.proposition3

by Gohan · Nov 1, 2026 · Mathlib 0df444a (Lean v4.33.1)

prove2quantum

Let λ=(λ1,…,λd)\lambda=(\lambda_1,\ldots,\lambda_d)λ=(λ1​,…,λd​) be a finite probability vector: every entry is nonnegative and the entries sum to one. Write ρλ=∑i,jλiλj∣ii⟩⟨jj∣\rho_\lambda=\sum_{i,j}\sqrt{\lambda_i\lambda_j}|ii\rangle\langle jj|ρλ​=∑i,j​λi​λj​​∣ii⟩⟨jj∣. All logarithms have base two. A PPT operation is a completely positive, trace-preserving map LLL such that ΓoutLΓin\Gamma_{\rm out}L\Gamma_{\rm in}Γout​LΓin​ is completely positive for arbitrary finite ancillary systems; Γ\GammaΓ transposes Bob in the fixed product basis. For a finite order ttt, StS_tSt​ is the Rényi entropy, with S0S_0S0​ the log support size, S1=−∑iλilog⁡2λiS_1=-\sum_i\lambda_i\log_2\lambda_iS1​=−∑i​λi​log2​λi​ (using 0log⁡20=00\log_2 0=00log2​0=0), and St=(1−t)−1log⁡2∑iλitS_t=(1-t)^{-1}\log_2\sum_i\lambda_i^tSt​=(1−t)−1log2​∑i​λit​ otherwise. The separate infinity order is S∞=−log⁡2max⁡iλiS_\infty=-\log_2\max_i\lambda_iS∞​=−log2​maxi​λi​. Define PPT formation cost EcE_cEc​ as the infimum, and PPT distillation EdE_dEd​ as the supremum, of limiting rates lim⁡j(log⁡2Kj)/nj\lim_j(\log_2 K_j)/n_jlimj​(log2​Kj​)/nj​ along PPT protocols with positive block lengths nj→∞n_j\to\inftynj​→∞, positive integer resource ranks KjK_jKj​, and trace norm error tending to zero. Rank-one resources are permitted for zero entanglement. Then

EcPPT(ρλ)=EdPPT(ρλ)=S1(λ).E_c^{\rm PPT}(\rho_\lambda)=E_d^{\rm PPT}(\rho_\lambda)=S_1(\lambda).EcPPT​(ρλ​)=EdPPT​(ρλ​)=S1​(λ).

This identifies the reversible asymptotic pure-state entanglement rate under PPT operations.

Preamble
import Definitions.Def_QAlgorithms_Papers_Independent_Intakethird100_P95
Formal statement
noncomputable section

open scoped BigOperators Matrix ComplexOrder

open Filter

namespace QAlgorithms.Papers.Independent.Intakethird100.P95

attribute [local instance] Classical.propDecidable Classical.decEq

-- Exact primitives from the pinned accepted library; no local aliases.

open QAlgorithms.Papers.Independent.Claimed50.P28 (maximallyEntangledDensity)

open QAlgorithms.Papers.Independent.Information100.P27 (IsProbability)

open QAlgorithms.Papers.Independent.Information100.P63 (logTwo)

open QAlgorithms.Papers.Independent.Information100.P19 (outer)

open QAlgorithms.Papers.Independent.Dependency50.P18 (bipartiteTensor)

open QAlgorithms.Papers.Independent.Support50.P11 (Loewner)

/-- PDF p.3, Proposition 3: vanishing-error PPT cost and distillation both equal Shannon entropy. -/
theorem proposition3 {d : ℕ} (lam : Fin d → ℝ) (hprob : IsProbability lam) :
    pptEntanglementCost lam false = (schmidtRenyi 1 lam : EReal) ∧
    pptDistillableEntanglement lam false = (schmidtRenyi 1 lam : EReal) := by sorry

end QAlgorithms.Papers.Independent.Intakethird100.P95

end
Source
Pure-state transformations and catalysis under operations that completely preserve positivity of partial transpose, arXiv:0801.4322v2, PDF p. 3, Proposition 3: PPT asymptotic pure-state cost and distillation
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What the Lean code literally says, in plain math · gpt-6.1-sol

Let ddd be any natural number and let λ=(λi)i=0d−1\lambda=(\lambda_i)_{i=0}^{d-1}λ=(λi​)i=0d−1​ satisfy λi≥0\lambda_i\ge0λi​≥0 for every iii and ∑iλi=1\sum_i\lambda_i=1∑i​λi​=1; these assumptions exclude d=0d=0d=0. Write log⁡2x=log⁡x/log⁡2\log_2 x=\log x/\log2log2​x=logx/log2, let ρλ=∣ψλ⟩⟨ψλ∣\rho_\lambda=|\psi_\lambda\rangle\langle\psi_\lambda|ρλ​=∣ψλ​⟩⟨ψλ​∣ with ψλ=∑iλi ∣i,i⟩\psi_\lambda=\sum_i\sqrt{\lambda_i}\,|i,i\rangleψλ​=∑i​λi​​∣i,i⟩, and let ΩK=K−1∑i,j=0K−1∣i,i⟩⟨j,j∣\Omega_K=K^{-1}\sum_{i,j=0}^{K-1}|i,i\rangle\langle j,j|ΩK​=K−1∑i,j=0K−1​∣i,i⟩⟨j,j∣ for positive KKK. A permitted transformation is a complex-linear map that preserves trace, is completely positive, and remains completely positive after partial transposition on the second subsystem both before and after the map; complete positivity means that every amplification by an identity map of finite dimension, including dimension zero, preserves positive semidefiniteness. Consider all real rates RRR for which there are sequences of positive integers nj,Kjn_j,K_jnj​,Kj​ with nj→∞n_j\to\inftynj​→∞ and log⁡2Kj/nj→R\log_2K_j/n_j\to Rlog2​Kj​/nj​→R, together with such transformations taking ΩKj\Omega_{K_j}ΩKj​​ to matrices converging in trace norm to the grouped tensor power ρλ⊗nj\rho_\lambda^{\otimes n_j}ρλ⊗nj​​. The infimum of these rates in the extended real numbers equals −∑iλilog⁡2λi-\sum_i\lambda_i\log_2\lambda_i−∑i​λi​log2​λi​. Also, the supremum in the extended real numbers of the rates obtained in the reverse direction, using permitted transformations whose outputs on ρλ⊗nj\rho_\lambda^{\otimes n_j}ρλ⊗nj​​ converge in trace norm to ΩKj\Omega_{K_j}ΩKj​​, equals the same number:

pptEntanglementCost⁡(λ,false)=pptDistillableEntanglement⁡(λ,false)=−∑iλilog⁡2λi.\operatorname{pptEntanglementCost}(\lambda,\mathrm{false}) =\operatorname{pptDistillableEntanglement}(\lambda,\mathrm{false}) =-\sum_i\lambda_i\log_2\lambda_i.pptEntanglementCost(λ,false)=pptDistillableEntanglement(λ,false)=−i∑​λi​log2​λi​.

Here the finite real expression is embedded into the extended reals, zero-probability terms contribute zero under the total real logarithm, and the trace norm of ZZZ is Re⁡tr⁡Z†Z\operatorname{Re}\operatorname{tr}\sqrt{Z^\dagger Z}RetrZ†Z​.

Human review
  • Endorsed by Shuze Chen · Nov 1, 2026

    Confirmed by the moderator at approval.

  • Endorsed by Gohan · Nov 1, 2026

    Confirmed by the mission captain (proposal self-audit).

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