Quantum Rotation Diversity in Displaced Squeezed Binary Phase-Shift Keying

TL;DR

This paper introduces a quantum rotation diversity scheme for optical quantum communication that enhances robustness against turbulence by redistributing displacement amplitude, achieving higher diversity orders and improved error performance.

Contribution

The paper presents a novel QRD scheme using displaced squeezed states and homodyne detection, with analytical performance expressions and optimal parameter settings, demonstrating super-diversity effects.

Findings

Achieves a diversity order of two under independent fading.

Derives closed-form optimal rotation angle and energy allocation.

Demonstrates super-diversity with combined displacement and squeezing scaling.

Abstract

We propose a quantum rotation diversity (QRD) scheme for optical quantum communication using binary phase-shift-keying displaced squeezed states and homodyne detection over Gamma-Gamma turbulence channels. Consecutive temporal modes are coupled by a passive orthogonal rotation that redistributes the displacement amplitude between slots, yielding a diversity order of two under independent fading and joint maximum-likelihood detection. Analytical expressions for the symbol-error rate performance, along with asymptotic results for the diversity and coding gains, are derived. The optimal rotation angle and energy allocation between displacement and squeezing are obtained in closed form. Furthermore, we show that when both the displacement amplitude and the squeezing strength scale with the total photon number, an effective diversity order of four is achieved. Numerical results validate the analysis and demonstrate the super-diversity behaviour of the proposed QRD scheme.