Every entangled state provides an advantage in classical communication

TL;DR

This paper demonstrates that all entangled states, including bound entangled states, can enhance classical communication capacity in quantum channels, revealing a fundamental link between entanglement and communication advantage.

Contribution

It shows that every entangled state can increase classical capacity in certain quantum channels, including those with bound entanglement, and provides an entropic criterion for this advantage.

Findings

All entangled states can enhance classical communication in some quantum channels.

Bound entangled states can provide communication advantages despite being non-distillable.

An entropic condition acts as an entanglement witness for communication advantage.

Abstract

We investigate the use of noisy entanglement as a resource in classical communication via a quantum channel. In particular, we are interested in the question whether for any entangled state, including bound entangled states, there exists a quantum channel the classical capacity of which can be increased by providing the state as an additional resource. We partially answer this question by showing, for any entangled state, the existence of a quantum memory channel the feedback-assisted classical capacity with product encodings of which can be increased by using the state as a resource. Using a different (memoryless) channel construction, we also provide a sufficient entropic condition for an advantage in classical communication (without feedback and for general encodings) and thus provide an example of a state that is not distillable by means of one-way local operations and classical communication (LOCC), but can provide an advantage in the classical capacity of a number of quantum channels. As separable states cannot provide an advantage in classical communication, our condition also provides an entropic entanglement witness.