QPSK coherent state discrimination via a hybrid receiver

TL;DR

This paper introduces a hybrid receiver scheme for QPSK state discrimination that outperforms standard heterodyne detection, especially for weak signals, demonstrated through theoretical analysis and experimental validation.

Contribution

The paper presents a novel hybrid receiver design for QPSK discrimination that achieves near-optimal performance and surpasses existing methods for highly attenuated signals.

Findings

Hybrid scheme outperforms heterodyne detection across all signal amplitudes.

Experimental results confirm theoretical predictions.

Achieves best performance for highly attenuated signals.

Abstract

We propose and experimentally demonstrate a near-optimal discrimination scheme for the quadrature phase shift keying protocol (QPSK). We show in theory that the performance of our hybrid scheme is superior to the standard scheme - heterodyne detection - for all signal amplitudes and underpin the predictions with our experimental results. Furthermore, our scheme provides the hitherto best performance in the domain of highly attenuated signals. The discrimination is composed of a quadrature measurement, a conditional displacement and a threshold detector.