Experimental Demonstration of a Heterogeneous Continuous-Variable Quantum Key Distribution via Hybrid Access Network

Abstract Continuous-variable quantum key distribution (CVQKD) is a highly promising method for building large-scale quantum networks due to its low cost and high capacity. However, current access networks involve hybrid channels and multiple users, where traditional CVQKD protocols may face limitations in performance. At the same time, as an emerging protocol, quantum key distribution with basis-encoding (BE-QKD) is compatible with traditional CVQKD protocols and has the potential to be applied in CVQKD access networks to provide performance advantages. But the performance of the BE-QKD protocol in current CVQKD access networks has not yet been fully exploited. In this work, we conduct an experimental demonstration of a heterogeneous continuous-variable quantum access network, which is based on the BE-QKD protocol with quadrature phase shift keying (QPSK) modulation and the traditional QPSK-CVQKD protocol. In addition, practical CVQKD access networks may involve different types of transmission links. Therefore, this access network is configured with four users, including two free-space channels and two fiber channels, to verify the feasibility of the proposed heterogeneous quantum access network scheme in a hybrid-channel environment. The experimental results demonstrate that the QPSK-BE-QKD protocol offers potential performance advantages across various channel scenarios in quantum access networks, such as the ability to withstand channel loss and secret key rates. And its compatibility with QPSK-CVQKD is confirmed. The proposed scheme is easy to deploy in existing CVQKD access networks and demonstrates significant performance potential, offering a new implementation paradigm for large-scale access scenario of CVQKD networks with complex and hybrid channels.