Displacement-Squeeze receiver for BPSK displaced squeezed vacuum states surpassing the coherent-states Helstrom bound under imperfect conditions

• URL: http://arxiv.org/abs/2601.09073v1
• Date: Wed, 14 Jan 2026 02:05:26 GMT
• Title: Displacement-Squeeze receiver for BPSK displaced squeezed vacuum states surpassing the coherent-states Helstrom bound under imperfect conditions
• Authors: Enhao Bai, Jian Peng, Tianyi Wu, Kai Wen, Fengkai Sun, Chun Zhou, Yaping Li, Zhenrong Zhang, Chen Dong,
• Abstract summary: displacement-squeeze receiver (DSR) for discriminating BPSK displaced squeezed vacuum states (S-BPSK)<n>We show that for all signal energy N, $P_texterrtextDSR in left[P_textHBtextDSS, 2P_textHBtextDSS right]$, under equal priors and ideal condition.<n>We quantify performance under non-unit efficiency and dark counts, phase diffusion, and receiver thermal noise, with MAP threshold adaptation providing robustness across these nonidealities.
• Score: 18.54481311613931
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: We propose a displacement-squeeze receiver (DSR) for discriminating BPSK displaced squeezed vacuum states (S-BPSK). The receiver applies a displacement followed by a squeezing operation with the squeezing axis rotated by $\fracπ{2}$, and performs photon-number-resolving detection with a MAP threshold decision. This processing effectively increases the distinguishability of the input states by elongating their distance in phase space and reducing their population overlap in Fock basis. We show that for all signal energy N, $P_\text{err}^\text{DSR} \in \left[P_\text{HB}^\text{DSS}, 2P_\text{HB}^\text{DSS}\right]$, under equal priors and ideal condition. In the low-energy regime, DSR beats the S-BPSK SQL at $N \approx 0.3$ and drops below the coherent-state BPSK (C-BPSK) Helstrom bound at $N \approx 0.4$, reaching $P_\text{err}^\text{DSR} < 1\%$ near $N \approx 0.6$. Finally, we quantify performance under non-unit efficiency and dark counts, phase diffusion, and receiver thermal noise, with MAP threshold adaptation providing robustness across these nonidealities.

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