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arXiv:2308.04146 · Physical Review A

Beating the standard quantum limit for binary phase-shift-keying discrimination with a realistic hybrid feed-forward receiver

Michele N. Notarnicola, Stefano Olivares

Published Oct 24, 2023• 11 citations
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Abstract

We propose a hybrid feed-forward receiver (HFFRE) for the discrimination of binary phase-shift-keyed coherent states based on the appropriate combination of a displacement feed-forward receiver (DFFRE) and a homodynelike setup employing a low-intensity local oscillator and photon-number-resolving detectors. We investigate the performance of the proposed scheme, also addressing realistic scenarios in the presence of nonunit quantum detection efficiency, dark counts, and visibility reduction. The present HFFRE outperforms the DFFRE in all conditions, beating the standard quantum limit in particular regimes.

DOI
10.1103/physreva.108.042619

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We propose a hybrid feed-forward receiver (HFFRE) for the discrimination of binary phase-shift-keyed coherent states based on the appropriate combination of a displacement feed-forward receiver (DFFRE) and a homodynelike setup employing a low-intensity local oscillator and photon-number-resolving detectors. We investigate the performance of the proposed scheme, also addressing realistic scenarios in the presence of nonunit quantum detection efficiency, dark counts, and visibility reduction. The present HFFRE outperforms the DFFRE in all conditions, beating the standard quantum limit in particular regimes.
We propose a near-optimum receiver for the discrimination of binary phase-shift-keyed coherent states employing photon-number-resolving detectors. The receiver exploits a discrimination strategy based on both so-called homodyne-like and direct detection, thus resulting in a hybrid scheme. We analyze the performance and robustness of the proposed scheme under realistic conditions, namely, in the presence of inefficient detection and dark counts. We show that the present hybrid setup is near- optimum and beats both the standard quantum limit and the performance of the Kennedy receiver.
This paper proposes a hybrid receiver, the heterodyne-like feedforward partitioned-displacement hybrid (HFPH) receiver, for discriminating quadrature phase-shift keying (QPSK) coherent states using photon-number-resolving (PNR) detectors. The receiver integrates a heterodyne-like (HL) measurement scheme with a Shuro-like (SL) displacement backend, forming a feedforward architecture that dynamically adapts to real-time decisions. We theoretically analyze the performance of the proposed scheme under practical imperfections, including detection inefficiency, dark counts, and imperfect interference visibility. Our results demonstrate that the HFPH receiver can surpass the standard quantum limit under these non-ideal conditions and exhibits enhanced robustness compared to the benchmark receiver.
We address the problem of coherent state discrimination in the presence of phase diffusion. We investigate the role of the HYbrid Near-Optimum Receiver (HYNORE) we proposed in [J. Opt. Soc. Am. B 40 (2023) 705] in the task of mitigating the noise impact. We prove the HYNORE to be a robust receiver, outperforming the Displacement Photon-Number-Resolving (DPNR) receiver and beating the standard quantum limit in particular regimes. We introduce the maximum tolerable phase noise [Formula: see text] as a figure of merit for the receiver robustness and show that HYNORE increases its value with respect to the DPNR receiver.
Over the past decade, binary phase-shift-keying encoding has been used as a benchmark to test the performance of different detection strategies to address the problem of state discrimination. In this context, hybrid devices, giving access to both particle- and wave-like properties of light, could offer the possibility to better discriminate the sent signals. In this work, we consider a quantum channel exploiting a hybrid receiver embedding Silicon photomultipliers as photon-number-resolving detectors. We retrieve the discrimination error probability and the mutual information between sender and receiver as functions of some relevant experimental parameters in the case of binary phase-shifted coherent states. Our promising results, supported also with numerical simulations and theoretical analysis, foster further using this kind of hybrid receiver in more complex detection schemes. • We address state discrimination by a Silicon photomultiplier-based hybrid receiver. • The hybrid receiver gives access to particle- and wave-like properties of light. • We consider error probability and mutual information in a BPSK scenario.
We present a quantum receiver for quadrature amplitude modulation (QAM) coherent-state discrimination with the homodyne-displacement hybrid structure. Our strategy is to carry out two successive measurements on parts of the quantum states. The homodyne result of the first measurement reveals partial information about the state and is forwarded to a displacement receiver, which finally identifies the input state by using feedback to adjust a reference field. Theoretical analysis and numerical simulation results show that for 16-QAM, the hybrid receiver could outperform the standard quantum limit using only on-off single-photon detectors with a reduced number of signal-state partitions, showing great potential toward implementing the receiver practically.
The quantum receiver is an important tool for overcoming the standard quantum limit (SQL) of discrimination errors in optical communication. We theoretically study the quantum receivers for discriminating ternary and quaternary phase-shift-keying coherent states in terms of average error rate and mutual information. Our receiver consists of on-off--type photon detectors and displacement operations without electrical feedforward operations. We show that for the ternary signals, the receiver shows a reasonable gain from the SQL even without feedforward. This scheme is realizable with the currently available technology. For the quaternary signals feedforward operation is crucial to overcome the SQL with imperfect devices. We also analytically examine the asymptotic limit of the performance of the proposed receiver with respect to the number of feedforward steps.