All-Gaussian State Discrimination Beyond the Coherent Helstrom Bound

Fuente: arXiv
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Main Authors: Walsh, Angus, Conlon, Lorcan, Shajilal, Biveen, Erkilic, Ozlem, Janousek, Jiri, Assad, Syed, Zhao, Jie, Lam, Ping Koy
Format: Preprint
Published: 2025
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author Walsh, Angus
Conlon, Lorcan
Shajilal, Biveen
Erkilic, Ozlem
Janousek, Jiri
Assad, Syed
Zhao, Jie
Lam, Ping Koy
author_facet Walsh, Angus
Conlon, Lorcan
Shajilal, Biveen
Erkilic, Ozlem
Janousek, Jiri
Assad, Syed
Zhao, Jie
Lam, Ping Koy
contents A core problem in communications is the optimal discrimination of binary-phase-shift-keyed (BPSK) signals. A longstanding goal has been to reach the fundamental quantum limit, known as the Helstrom bound, for BPSK signals encoded in coherent states. However, due to technical constraints, proposals for reaching the bound remain impractical. In this letter we take an alternative approach: using only Gaussian optics - displaced squeezed states and homodyne detection - we achieve discrimination of BPSK signals with error rates below what can be achieved using coherent states and any quantum measurement.
format Preprint
id arxiv_https___arxiv_org_abs_2510_20096
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle All-Gaussian State Discrimination Beyond the Coherent Helstrom Bound
Walsh, Angus
Conlon, Lorcan
Shajilal, Biveen
Erkilic, Ozlem
Janousek, Jiri
Assad, Syed
Zhao, Jie
Lam, Ping Koy
Quantum Physics
A core problem in communications is the optimal discrimination of binary-phase-shift-keyed (BPSK) signals. A longstanding goal has been to reach the fundamental quantum limit, known as the Helstrom bound, for BPSK signals encoded in coherent states. However, due to technical constraints, proposals for reaching the bound remain impractical. In this letter we take an alternative approach: using only Gaussian optics - displaced squeezed states and homodyne detection - we achieve discrimination of BPSK signals with error rates below what can be achieved using coherent states and any quantum measurement.
title All-Gaussian State Discrimination Beyond the Coherent Helstrom Bound
topic Quantum Physics
url https://arxiv.org/abs/2510.20096