Non-Orthogonal Multiple Access-Based Continuous-Variable Quantum Key Distribution: Secret Key Rate Analysis and Power Allocation

TL;DR

This paper introduces a NOMA-based continuous-variable QKD system that maximizes secret key rates for multiple users under attacks, using novel power allocation and theoretical bounds, enhancing performance and robustness.

Contribution

It proposes a new NOMA-CVQKD system with a power allocation algorithm and derives asymptotic bounds for key rates under collective attacks, advancing multi-user quantum communication.

Findings

Achieves up to 23% higher sum SKR than OMA-based systems.

Supports 16 users at excess noise variance 0.1.

Remains robust under turbulence and varying distances.

Abstract

We address the multi-user quantum key distribution (QKD) problem under malicious quantum attacks, which is critical for realizing a large-scale quantum Internet. This paper maximizes the sum secret key rate (SKR) of a novel uplink non-orthogonal multiple access based continuous-variable QKD (NOMA-CVQKD) system under collective attacks. The proposed system uses Gaussian-modulated coherent states and a quantum successive interference cancellation based heterodyne receiver. We derive closed-form asymptotic bounds for the legitimate users' achievable key rates via the entropy power inequality and maximum entropy principle, as well as for the eavesdropper's intercepted information based on Holevo information. A successive convex approximation based power allocation algorithm is developed to maximize the asymptotic sum SKR of the NOMA-CVQKD system under collective attacks, with guaranteed convergence to a locally optimal Karush-Kuhn-Tucker solution. Simulation results show that the proposed NOMA-CVQKD system with the power allocation algorithm achieves up to 23% higher sum SKR than quantum-orthogonal multiple access, supports 16 users at excess noise variance 0.1, and remains robust under varying turbulence intensities and transmission distances.