Multi-Phase Hadamard receivers for classical communication on lossy bosonic channels

TL;DR

This paper introduces a multi-phase Hadamard receiver scheme for classical communication over lossy bosonic channels, achieving near-capacity rates with practical detection methods in certain regimes.

Contribution

It generalizes previous proposals by incorporating multiple phases and passive transformations, and proposes a feasible receiver that improves performance in intermediate photon-number regimes.

Findings

Achieves classical capacity in low energy regime with optimal detection.

Proposes a practical receiver based on conditional Dolinar detection.

Shows improvements over previous schemes in intermediate photon-number regimes.

Abstract

A scheme for transferring classical information over a lossy bosonic channel is proposed by generalizing the proposal presented in Phys. Rev. Lett. 106, 240502 (2011) by Guha. It employs codewords formed by products of coherent states of fixed mean photon number with multiple phases which, through a passive unitary transformation, reduce to a Pulse-Position Modulation code with multiple pulse phases. The maximum information rate achievable with optimal, yet difficult to implement, detection schemes is computed and shown to saturate the classical capacity of the channel in the low energy regime. An easy to implement receiver based on a conditional Dolinar detection scheme is also proposed finding that, while suboptimal, it allows for improvements in an intermediate photon-number regime with respect to previous proposals.