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Strict separation between regularized Rains and PPT relative entropy

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QAlgorithms.Papers.Independent.Intakethird100.P90.rhoV_strict_separation

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

prove2quantum

All systems are finite-dimensional complex Hilbert spaces with fixed orthonormal product bases and positive local dimensions. A state is a positive semidefinite operator of trace one. All logarithms are base two and all operational rates are measured in standard Bell pairs (ebits) per input copy, with deterministic operations and error tending to zero. Write ED,ECE_D,E_CED​,EC​ for distillable entanglement and entanglement cost under completely PPT-preserving CPTP operations; an explicit LOCC subscript denotes unrestricted two-way local operations and classical communication.

Let ρv\rho_vρv​ be the equal mixture of the unit antisymmetric kets (∣01⟩−∣10⟩)/2(|01\rangle-|10\rangle)/\sqrt2(∣01⟩−∣10⟩)/2​ and (∣02⟩−∣20⟩)/2(|02\rangle-|20\rangle)/\sqrt2(∣02⟩−∣20⟩)/2​. Let R∞R^\inftyR∞ be the positive-block regularization of the Rains bound and ER∞E_R^\inftyER∞​ that of relative entropy to normalized PPT states. Then

ED(ρv)=R∞(ρv)<ER∞(ρv)=EC(ρv).E_D(\rho_v)=R^\infty(\rho_v)<E_R^\infty(\rho_v)=E_C(\rho_v).ED​(ρv​)=R∞(ρv​)<ER∞​(ρv​)=EC​(ρv​).

This is the full equality/strict-inequality/equality chain announced as the main contribution in Eq. (3).

Preamble
import Definitions.Def_QAlgorithms_Papers_Independent_Intakethird100_P90
Formal statement
noncomputable section

open scoped Matrix ComplexConjugate ComplexOrder

namespace QAlgorithms.Papers.Independent.Intakethird100.P90

attribute [local instance] Classical.propDecidable Classical.decEq

open QAlgorithms

open QAlgorithms.Papers.Independent.Dependency50.P36
  (relativeEntropy rains target canonicalMatrix allowed pptDistillable)

open QAlgorithms.Papers.Independent.Information100.P04 (gamma copies IsPPT)

open QAlgorithms.Papers.Independent.Next46.P42 (regroupProduct)

open QAlgorithms.Papers.Independent.Information100.P06 (supportProjection)

open QAlgorithms.Papers.Independent.Information100.P21 (FiniteLOCC)

open QAlgorithms.Papers.Independent.Gap48.P32 (antisymmetricQutrit)

/-- arXiv:1606.09421v3, PDF p.2, Eq.(3): preserve the full strict chain. -/
theorem rhoV_strict_separation :
    pptDistillable rhoV = regularizedRains rhoV ∧
    regularizedRains rhoV < regularizedPptRelativeEntropy rhoV ∧
    regularizedPptRelativeEntropy rhoV = asymptoticEntanglementCost false rhoV := by sorry

end QAlgorithms.Papers.Independent.Intakethird100.P90

end
Source
Irreversibility of Asymptotic Entanglement Manipulation Under Quantum Operations Completely Preserving Positivity of Partial Transpose, arXiv:1606.09421v3, PDF p. 2, Unnumbered main result, Eq.(3): strict regularized Rains/relative-entropy separation
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What the Lean code literally says, in plain math · gpt-6.1-sol

Let vj=(∣0,j⟩−∣j,0⟩)/2v_j=(|0,j\rangle-|j,0\rangle)/\sqrt2vj​=(∣0,j⟩−∣j,0⟩)/2​ for j=1,2j=1,2j=1,2, using coordinate basis kets on {0,1,2}×{0,1,2}\{0,1,2\}\times\{0,1,2\}{0,1,2}×{0,1,2}, and let ρV=12(v1v1†+v2v2†)\rho_V=\tfrac12(v_1v_1^\dagger+v_2v_2^\dagger)ρV​=21​(v1​v1†​+v2​v2†​), with outer-product entries vxvy‾v_x\overline{v_y}vx​vy​​. The assertion is the extended-real conjunction

DPPT(ρV)=R∞(ρV),R∞(ρV)<EPPT∞(ρV),EPPT∞(ρV)=CPPT(ρV).D_{\mathrm{PPT}}(\rho_V)=R^\infty(\rho_V),\qquad R^\infty(\rho_V)<E_{\mathrm{PPT}}^\infty(\rho_V),\qquad E_{\mathrm{PPT}}^\infty(\rho_V)=C_{\mathrm{PPT}}(\rho_V).DPPT​(ρV​)=R∞(ρV​),R∞(ρV​)<EPPT∞​(ρV​),EPPT∞​(ρV​)=CPPT​(ρV​).

Here Γ\GammaΓ transposes the second party, (ΓX)(a,b),(a′,b′)=X(a,b′),(a′,b)(\Gamma X)_{(a,b),(a',b')}=X_{(a,b'),(a',b)}(ΓX)(a,b),(a′,b′)​=X(a,b′),(a′,b)​, and ∥X∥1=Re⁡Tr⁡X†X\|X\|_1=\operatorname{Re}\operatorname{Tr}\sqrt{X^\dagger X}∥X∥1​=ReTrX†X​. Define D2(X∥S)=Re⁡Tr⁡(Xlog⁡X−Xlog⁡S)/log⁡2D_2(X\|S)=\operatorname{Re}\operatorname{Tr}(X\log X-X\log S)/\log2D2​(X∥S)=ReTr(XlogX−XlogS)/log2 when ker⁡S⊆ker⁡X\ker S\subseteq\ker XkerS⊆kerX, and +∞+\infty+∞ otherwise, using spectral functional calculus and log⁡0=0\log0=0log0=0. Then

R∞(ρV)=inf⁡n≥11ninf⁡S≥0∥ΓS∥1≤1D2(ρV⊗n∥S),EPPT∞(ρV)=inf⁡n≥11ninf⁡S≥0, Tr⁡S=1ΓS≥0D2(ρV⊗n∥S).R^\infty(\rho_V)=\inf_{n\ge1}\frac1n \inf_{\substack{S\ge0\\\|\Gamma S\|_1\le1}}D_2(\rho_V^{\otimes n}\|S), \qquad E_{\mathrm{PPT}}^\infty(\rho_V)=\inf_{n\ge1}\frac1n \inf_{\substack{S\ge0,\ \operatorname{Tr}S=1\\\Gamma S\ge0}}D_2(\rho_V^{\otimes n}\|S).R∞(ρV​)=n≥1inf​n1​S≥0∥ΓS∥1​≤1​inf​D2​(ρV⊗n​∥S),EPPT∞​(ρV​)=n≥1inf​n1​S≥0, TrS=1ΓS≥0​inf​D2​(ρV⊗n​∥S).

A channel is a finite Kraus sum X↦∑jKjXKj†X\mapsto\sum_jK_jXK_j^\daggerX↦∑j​Kj​XKj†​ with ∑jKj†Kj=I\sum_jK_j^\dagger K_j=I∑j​Kj†​Kj​=I, and it is PPT if its input-output partial-transpose conjugate is also a channel. The quantity DPPT(ρV)D_{\mathrm{PPT}}(\rho_V)DPPT​(ρV​) is the supremum of real r≥0r\ge0r≥0 such that, for every ε>0\varepsilon>0ε>0, all sufficiently large natural nnn admit a PPT channel mapping ρV⊗n\rho_V^{\otimes n}ρV⊗n​ within trace norm ε\varepsilonε of Φ⌈2nr⌉\Phi_{\lceil2^{nr}\rceil}Φ⌈2nr⌉​. The quantity CPPT(ρV)C_{\mathrm{PPT}}(\rho_V)CPPT​(ρV​) is the infimum of real r≥0r\ge0r≥0 such that, for every ε,δ>0\varepsilon,\delta>0ε,δ>0, all sufficiently large positive natural nnn admit m∈Nm\in\mathbb Nm∈N and a PPT channel mapping Φ2m\Phi_{2^m}Φ2m​ within trace norm ε\varepsilonε of ρV⊗n\rho_V^{\otimes n}ρV⊗n​, with m≤n(r+δ)m\le n(r+\delta)m≤n(r+δ). The matrix Φk\Phi_kΦk​ has entry 1/k1/k1/k when both row and column have equal party indices and 000 otherwise; tensor-power entries are products, party registers are grouped and relabelled by fixed finite-index bijections, and m=0m=0m=0 is included.

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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