Single-shot discrimination of coherent states beyond the standard quantum limit

TL;DR

This paper demonstrates a single-shot method using a photon-number-resolving detector to discriminate coherent states beyond the standard quantum limit, significantly improving quantum communication efficiency.

Contribution

The work introduces a novel single-shot discrimination technique that surpasses the SQL using a transition-edge sensor, without requiring measurement feedback.

Findings

Achieved up to 7.7 dB improvement over SQL

Effective for signals with up to seven photons on average

Compatible with high-bandwidth quantum communication

Abstract

The discrimination of coherent states is a key task in optical communication and quantum key distribution protocols. In this work, we use a photon-number-resolving detector, the transition-edge sensor, to discriminate binary-phase-shifted coherent states at a telecom wavelength. Owing to its dynamic range and high efficiency, we achieve a bit error probability that unconditionally exceeds the standard quantum limit (SQL) by up to 7.7 dB. The improvement to the SQL persists for signals containing up to approximately seven photons on average and is achieved in a single shot (i.e. without measurement feedback), thus making our approach compatible with larger bandwidths.