The Multiple-Access Channel with Entangled Transmitters

TL;DR

This paper investigates the capacity region of classical multiple-access channels with pre-shared entanglement, establishing bounds and showing how entanglement can enhance communication rates, especially when combined with conferencing.

Contribution

It provides the first general bounds on the capacity region for MACs with entangled transmitters and demonstrates how entanglement can improve communication, including in conferencing scenarios.

Findings

Entanglement can strictly increase the sum rate in MACs.

The capacity regions with entanglement and without coincide under certain error criteria.

Superdense coding enables doubling of conferencing rates with entanglement.

Abstract

Communication over a classical multiple-access channel (MAC) with entanglement resources is considered, whereby two transmitters share entanglement resources a priori before communication begins. Leditzky et al. (2020) presented an example of a classical MAC, defined in terms of a pseudo telepathy game, such that the sum rate with entangled transmitters is strictly higher than the best achievable sum rate without such resources. Here, we establish inner and outer bounds on the capacity region for the general MAC with entangled transmitters, and show that the previous result can be obtained as a special case. It has long been known that the capacity region of the classical MAC under a message-average error criterion can be strictly larger than with a maximal error criterion (Dueck, 1978). We observe that given entanglement resources, the regions coincide. Furthermore, we address the combined setting of entanglement resources and conferencing, where the transmitters can also communicate with each other over rate-limited links. Using superdense coding, entanglement can double the conferencing rate.