Phase noise in collective binary phase shift keying with Hadamard words

TL;DR

This paper investigates how phase noise affects an optical communication scheme using collective detection of binary coherent states with Hadamard words, showing that superadditivity of information is preserved despite phase fluctuations.

Contribution

It demonstrates that the superadditive spectral efficiency in collective detection schemes remains robust under realistic phase noise conditions.

Findings

Superadditivity of spectral efficiency is maintained with phase noise.

Phase fluctuations around a fixed reference do not destroy the scheme's advantages.

The analysis confirms robustness of collective detection in practical noisy environments.

Abstract

We analyze the effect of phase fluctuations in an optical communication scheme based on collective detection of sequences of binary coherent state symbols using linear optics and photon counting. When the phase noise is absent, the scheme offers qualitatively improved nonlinear scaling of the spectral efficiency with the mean photon number in the low-power regime compared to individual detection. We show that this feature, providing a demonstration of superaddivitity of accessible information in classical communication over quantum channels, is preserved if random phases imprinted on transmitted symbols fluctuate around a reference fixed over the sequence length.