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Updated: May 29, 2025

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Fundamental Limit on the Power of Entanglement Assistance in Quantum Communication
Lasse H Wolff1, Paula Belzig2, Matthias Christandl1
1University of Copenhagen, Department of Mathematical Sciences, Universitetsparken 5, 2100 Denmark.
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(d^{2}), where d is the input dimension of the channel. An application to quantum communication with noisy encoders and decoders is given.
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