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arXiv · 2607.16960

Entanglement Quantification via Symmetric Extensions: A Resource Theory Hierarchy

Enmin Shao·Lin Chen·Huixia He
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Abstract

We introduce a hierarchy of entanglement measures Ek based on k-symmetric PPT extensions. Each Ek, defined via a minimal eigenvalue shift and computed by semidefinite programming, is faithful, convex, and monotone under free operations. The hierarchy strictly refines PPT-robustness at k = 1, detects bound entanglement at k = 2, and converges exactly to the separability measure as k -> infinity. Numerical experiments on Horodecki, Werner, UPB, and random states demonstrate practical scalability. Our framework unifies computational efficiency with operational fidelity in a single tunable family -- a combination previously believed to be fundamentally incompatible in entanglement quantification. It supplies, for the first time, a systematically improvable resource-theoretic yardstick that accounts for all entangled states, including the bound entangled ones that have long resisted quantitative treatment.

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Enmin Shao, Lin Chen, Huixia He. 2026-07-18. Entanglement Quantification via Symmetric Extensions: A Resource Theory Hierarchy. https://arxiv.org/abs/2607.16960

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