The Minimal Dimension of Entangled-Noise Advantage

arXiv:2609.28367 · quant-ph · Submitted 2026-09-23 · Read on arXiv

quant-ph

Submitted: 2026-09-23

Updated: 2026-09-23

Comments: 32 pages, 4 figures

Code: https://github.com/Hronrad/entangled-noise-certificates

License: http://creativecommons.org/licenses/by-nc-nd/4.0/

The gist: Can entangled noise erase entanglement more efficiently than separable noise? Standard robustness restricts the added noise to separable states; generalized robustness allows any state.

Terminology

Abstract

Can entangled noise erase entanglement more efficiently than separable noise? Standard robustness restricts the added noise to separable states; generalized robustness allows any state. We prove that the two costs coincide for every two-qubit state and give an explicit full-rank qubit--qutrit state with a strict gap. Positivity under partial transpose (PPT) characterizes separability in both dimensions, so the boundary is not caused by a failure of the PPT criterion. Instead, product-vector geometry permits a rank-one bridge between the two-qubit dual optimizations and supplies a two-dimensional completely entangled subspace for the qubit--qutrit separation. Local isometric embeddings complete the finite-dimensional bipartite classification, also for any fixed multipartite cut. Combined with known three-qubit separation, the result classifies universal equality relative to full separability in all finite multipartite systems.

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