Partial decode-forward for quantum relay channels

TL;DR

This paper introduces a partial decode-forward strategy for quantum relay channels with classical inputs and quantum outputs, utilizing block-Markov coding and quantum measurements to enhance communication rates.

Contribution

It presents a novel partial decode-forward scheme with quantum measurements and a sliding-window decoding method for quantum relay channels.

Findings

Achieves non-trivial classical communication rates over quantum relay channels.

Introduces a block-Markov coding scheme with quantum measurements at the relay.

Develops a sliding-window quantum measurement technique for decoding.

Abstract

A relay channel is one in which a Source and Destination use an intermediate Relay station in order to improve communication rates. We propose the study of relay channels with classical inputs and quantum outputs and prove that a "partial decode and forward" strategy is achievable. We divide the channel uses into many blocks and build codes in a randomized, block-Markov manner within each block. The Relay performs a standard Holevo-Schumacher-Westmoreland quantum measurement on each block in order to decode part of the Source's message and then forwards this partial message in the next block. The Destination performs a novel "sliding-window" quantum measurement on two adjacent blocks in order to decode the Source's message. This strategy achieves non-trivial rates for classical communication over a quantum relay channel.