Multiple-quadrature-amplitude-modulation continuous-variable quantum key distribution realization with a downstream-access network

Abstract

Quantum networks based on quantum key distribution ensure the security which is guaranteed by the fundamental laws of quantum physics between multiple parties. The discrete-modulation (DM) continuous-variable quantum key distribution (CV-QKD) protocols have the characteristics of simple implementation and compatibility with classical digital communication, making them very suitable for deployment in large-scale communication networks. However, the actual communication network has a huge communication capacity and a large number of units. To solve this problem, we propose a multiple-quadrature-amplitude-modulation (MQAM) DM protocol with a numerical method and complete the security analysis of the DM protocol in a downstream-access network situation. By introducing an extra dimension of signal modulation, the high-order modulated MQAM protocol greatly improves the number of supported units and the key rate of each unit. We give the results of a 16 quadrature amplitude modulation CV-QKD protocol in a downstream-access network which achieves 64 supported network units even in the case of high excess noise, which shows the application prospects of high-order discrete-modulation CV-QKD in network security.