Fundamental Limit on the Power of Entanglement Assistance in Quantum Communication

Lasse H. Wolff, Paula Belzig, Matthias Christandl, Bergfinnur Durhuus, Marco Tomamichel

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Abstract

The optimal rate of reliable communication over a quantum channel can be enhanced by preshared entanglement. Whereas the enhancement may be unbounded in infinite-dimensional settings even when the input power is constrained, a long-standing conjecture asserts that the ratio between the entanglement-assisted and unassisted classical capacities is bounded in finite-dimensional settings [Bennett et al., IEEE Trans. Inf. Theory 48, 2637 (2002)IETTAW0018-944810.1109/TIT.2002.802612]. In this Letter, we prove this conjecture by showing that their ratio is upper bounded by o(d2), where d is the input dimension of the channel. An application to quantum communication with noisy encoders and decoders is given. © 2025 authors. Published by the American Physical Society.
Original languageEnglish
Article number020802
JournalPhysical Review Letters
Volume134
Issue number2
Number of pages7
ISSN0031-9007
DOIs
Publication statusPublished - 2025

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