Employing weak-field homodyne detection for quantum communications

TL;DR

This paper explores weak-field homodyne detection in quantum communication, demonstrating capacity enhancements in photon-starved regimes and improvements with non-Gaussian modulation, especially at low PNR resolution.

Contribution

It introduces the use of weak-field homodyne detection for quantum communication, showing capacity gains and performance improvements over traditional methods.

Findings

Enhanced mutual information over Shannon capacity in photon-starved regime.

Non-Gaussian modulation increases information rate, especially at low PNR resolution.

Performance benefits are more pronounced with intermediate energy and low PNR resolution.

Abstract

We investigate the role of weak-field homodyne (WF) measurement for quantum communications over a lossy bosonic channel with coherent state encoding. This kind of receiver employs photon-number resolving (PNR) detectors with finite resolution and low-intensity local oscillator. As a figure of merit, we consider the mutual information for a Gaussian input modulation. We prove an enhancement over Shannon capacity in the photon starved regime, obtained by exploiting information on the mean signal energy to suitably optimize the local oscillator intensity. Thereafter, we investigate the performance of non-Gaussian modulation, by considering a Gamma distribution of the energy of the encoded pulses, and achieve an increase in the information rate with respect to the Gaussian modulation case in the intermediate energy regime, being more accentuated for low values of the PNR resolution.