We numerically study the performance of the displacement based quantum receiver for the discrimination of weak 3- and 4-phase-shift keyed (PSK) coherent state signals. We show that due to the nontrivial asymmetry of the receiver structure, optimization of the prior probability increases the mutual information and achieves sub-shot-noise limit discrimination. Moreover, we estimate the cutoff rate for a 4-PSK signal and confirm that the prior probability optimization shortens the code length for a given decoding error criterion. Such consideration for the asymmetric channel matrix is essential in a study of the compassable quantum receiver.
@article{arxiv.1308.2036,
title = {Performance gain of displacement receiver with optimized prior probability},
author = {M. Fujiwara and S. Izumi and M. Takeoka and M. Sasaki},
journal= {arXiv preprint arXiv:1308.2036},
year = {2015}
}