Discrimination of the binary coherent signal: Gaussian-operation limit and simple non-Gaussian near-optimal receivers

TL;DR

This paper investigates the limits of Gaussian operations in quantum state discrimination, demonstrating homodyne detection as optimal for BPSK signals and proposing simple near-optimal non-Gaussian receivers that outperform traditional methods across all signal powers.

Contribution

It identifies the optimal Gaussian strategy for BPSK discrimination and introduces practical non-Gaussian receivers that surpass the homodyne limit without needing real-time feedback.

Findings

Homodyne detection is optimal among Gaussian strategies for BPSK.

Proposed non-Gaussian receivers outperform homodyne detection at all signal powers.

The scheme is simple and does not require real-time electrical feedback.

Abstract

We address the limit of the Gaussian operations and classical communication in the problem of quantum state discrimination. We show that the optimal Gaussian strategy for the discrimination of the binary phase shift keyed (BPSK) coherent signal is a simple homodyne detection. We also propose practical near-optimal quantum receivers that beat the BPSK homodyne limit in all areas of the signal power. Our scheme is simple and does not require realtime electrical feedback.