There are two main detection schemes considered in optical quantum communication: one exploiting the particle-like nature of the radiation (as on/off or photon-number-resolving detection), while the other accesses its wave-light nature (as homodyne, heterodyne or intradyne detection). The two schemes are based on rather different technologies and implementing them in the same communication channel may be challenging. We propose a hybrid near-optimum receiver, HYNORE, for the discrimination of binary phase-shift-keyed coherent states employing only photon-number-resolving detectors. HYNORE exploits a discrimination strategy based on both a homodyne-like (or weak-field homodyne) scheme using photon-number-resolving detectors [1, 2, 3] and the direct detection, thus resulting in a hybrid scheme. We analyse the performance and the robustness of HYNORE under realistic conditions, namely, in the presence of inefficient detection, dark counts and non-unit visibility. We show that HYNORE is near-optimum, namely, it exhibits a discrimination error probability proportional to the Helstrom bound, and beats both the standard-quantum-limit, achievable with (standard) homodyne detection alone and the performance of the near-optimum Kennedy receiver [4]. Application of HYNORE in feed-forward discrimination schemes is also considered [5].
References:
[1] A. Allevi, M. Bina, S. Olivares and M. Bondani, Int. J. Quant. Inf. 15, 1740016 (2017).
[2] M. Bina, A. Allevi, M. Bondani and S. Olivares, Opt. Express 25, 10685-10692 (2017).
[3] G. Donati, et al., Nature Comm. 5, 5584 (2014).
[4] M. N. Notarnicola, M. G. A. Paris and S. Olivares, J. Opt. Soc. Am. B 40, 705-714 (2023).
[5] M. N. Notarnicola and S. Olivares Phys. Rev. A 108, 042619 (2023).
