Beating the standard quantum limit for binary phase-shift-keying discrimination with a realistic hybrid feed-forward receiver

TL;DR

This paper introduces a hybrid feed-forward receiver that combines displacement and homodyne-like detection to improve binary phase-shift-keyed state discrimination, surpassing the standard quantum limit under realistic conditions.

Contribution

The paper presents a novel hybrid feed-forward receiver design that outperforms existing methods in binary phase-shift-keyed state discrimination, even with non-ideal detector efficiencies.

Findings

HFFRE outperforms DFFRE in all tested conditions.

HFFRE beats the standard quantum limit in specific regimes.

Performance remains robust with realistic detector imperfections.

Abstract

We propose a hybrid feed-forward receiver (HFFRE) for the discrimination of binary phase-shift-keyed coherent states based on the appropriate combination of a displacement feed-forward receiver (DFFRE) and a homodynelike setup employing a low-intensity local oscillator and photon-number-resolving detectors. We investigate the performance of the proposed scheme, also addressing realistic scenarios in the presence of nonunit quantum detection efficiency, dark counts, and visibility reduction. The present HFFRE outperforms the DFFRE in all conditions, beating the standard quantum limit in particular regimes.