To achieve the maximum information transfer and face a possible eavesdropper, the samples transmitted in continuous-variable quantum key distribution (CV-QKD) protocols are to be drawn from a continuous Gaussian distribution. As a matter of fact, in practical implementations the transmitter has a finite (power) dynamics and the Gaussian sampling can be only approximated. This requires the quantum protocols to operate at small powers. In this paper, we show that a suitable probabilistic amplitude shaping of a finite set of symbols allows to approximate at will the optimal channel capacity also for increasing average powers. We investigate the feasibility of this approach in the framework of CV-QKD, propose a protocol employing discrete quadrature amplitude modulation assisted with probabilistic amplitude shaping, and we perform the key generation rate analysis assuming a wiretap channel and lossless homodyne detection.
@article{arxiv.2211.05688,
title = {Probabilistic amplitude shaping for continuous-variable quantum key distribution with discrete modulation over a wiretap channel},
author = {Michele N. Notarnicola and Stefano Olivares and Enrico Forestieri and Emanuele Parente and Luca Potì and Marco Secondini},
journal= {arXiv preprint arXiv:2211.05688},
year = {2024}
}