Continuous-variable Quantum Key Distribution Access Network
Tao Wang, Yuehan Xu, Lang Li, Xu Liu, Zicong Tan, Peng Huang, Guihua Zeng · 2024
Quantum key distribution (QKD) networks are crucial for the development of quantum networks and the early stages of the quantum internet, enabling unconditional secure key distribution and guaranteeing data security. However, current QKD networks are still limited in their structure, and are hard to achieve super multi-user access due to high system costs associated with the original point-to-point QKD system. In this paper, we introduce two cost-effective continuous-variable QKD (CV-QKD) access network schemes. The first one is a round-trip multi-band CV-QKD access network. Specifically, the frequency division multiplexing (FDM) technology is used to support multi-user access, and the round-trip optical architecture is adopted to realize low cost. As a result of the encoding properties of CV-QKD, different users can utilize the quadrature components in various frequency bands to transmit key information. The proposed network theoretically supports hundreds of users and can be easily expanded using simple equipment. The second one is a CV-QKD access network based on directed detection. With the help of the Kramers-Kronig relation, the receiver at the optical network unit can obtain the quadrature components just using a photodetector. Besides, it can also solve the practical issues in the plug-and-play structure. Compared with a quantum access network based on the point-to-point QKD system, these two schemes can provide cost-effective solutions for the subsequent large-scale verification and implementation of quantum access networks.