Quantum receiver for phase-shift keying at the single photon level

TL;DR

This paper introduces a new quantum receiver for phase-shift keying that surpasses the standard quantum limit using only linear optics and on-off detection, enabling improved optical communication at low power levels.

Contribution

The work presents an experimentally demonstrated decoding scheme that outperforms all known non-adaptive detectors without requiring feed-forward operations.

Findings

Surpasses the standard quantum limit in decoding phase-shift keying signals.

Outperforms all previously known non-adaptive detectors at low input powers.

Uses only linear optical elements and on-off photo-detection, simplifying implementation.

Abstract

Quantum enhanced receivers are endowed with resources to achieve higher sensitivities than conventional technologies. For application in optical communications, they provide improved discriminatory capabilities for multiple non-orthogonal quantum states. In this work, we propose and experimentally demonstrate a new decoding scheme for quadrature phase-shift encoded signals. Our receiver surpasses the standard quantum limit and outperforms all previously known non-adaptive detectors at low input powers. Unlike existing approaches, the receiver only exploits linear optical elements and on-off photo-detection. This circumvents the requirement for challenging feed-forward operations that limit communication transmission rates and can be readily implemented with current technology.