Enhanced Simultaneous Quantum-Classical Communications Under Composable Security

TL;DR

This paper revises the analysis of simultaneous quantum-classical communication protocols in CV-QKD, addressing security issues, modeling channel coupling, and demonstrating improved performance and security in finite-key regimes.

Contribution

It introduces a new security analysis and model for SQCC in CV-QKD, showing enhanced quantum efficiency and composable security under realistic conditions.

Findings

Improved secret-key generation rate with optimized parameters

Enhanced quantum efficiency at given classical error rates

Retains quantum advantage in finite-key security regime

Abstract

Simultaneous quantum-classical communications (SQCC) protocols are a family of continuous-variable quantum key distribution (CV-QKD) protocols which allow for quantum and classical symbols to be integrated concurrently on the same optical pulse and mode. In this work, we present a revised analysis of simultaneous quantum-classical communications in Gaussian-modulated coherent-state CV-QKD protocols. We address security concerns inherently associated with SQCC schemes and provide an updated model of the coupling between the classical and quantum channels. We provide evidence for our model via Monte Carlo simulation. We compute the performance of our revised SQCC protocol in terms of the secret-key generation rate optimised over free parameters and demonstrate improved quantum efficiency for a given classical bit-error rate. Lastly, we extend our analysis into the finite-key regime, where we propose a scheme for composably-secure SQCC under realistic operating conditions and demonstrate that our scheme retains the advantage in quantum performance over previous models.