Quantum Rotation Diversity in Displaced Squeezed Binary Phase-Shift Keying

2026-01-26

IEEE Transactions on Quantum Engineering

AI Summary

This work proposes a quantum rotational diversity scheme to address the high symbol error rate and limited diversity gain in optical quantum communication over atmospheric turbulence channels. By introducing, for the first time, a rotational diversity mechanism into quantum communication, the scheme integrates displaced squeezed states, binary phase-shift keying, homodyne detection, and maximum-likelihood joint detection. It achieves super-diversity performance with an effective diversity order of four in Gamma–Gamma turbulence channels through passive orthogonal rotation coupling of continuous-time modes. The study derives closed-form expressions for the symbol error rate as well as asymptotic diversity and coding gains, and provides analytical solutions for the optimal rotation angle and energy allocation. Numerical simulations confirm that a fourth-order diversity gain is attainable under high-photon-number conditions.

Technology Category

• Machine Learning: Quantum Machine Learning
• Search and Optimization: Mixed Discrete/Continuous Search
• Reasoning under Uncertainty: Stochastic Optimization

Application Category

• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: LLM based quality controls for crowd work
• Search and Retrieval-Augmented AI: Retrieval-Augmented Generation (RAG) and multi-modal RAG

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.

Problem

• quantum communication
• atmospheric turbulence
• binary phase-shift keying
• squeezed states
• fading channels

Innovation

• Quantum Rotation Diversity
• Displaced Squeezed States
• Binary Phase-Shift Keying
• Gamma-Gamma Turbulence
• Super-Diversity