A cluster-based networking approach for large-scale and wide-area quantum key agreement

Quantum key distribution (QKD), a cryptographic technology developed to generate random secure keys, can realize unconditional secure remote classical communication in theory. However, QKD technology is currently confronted with two core problems: the extension of key distribution distance and the implementation of concurrent key agreements between multiple pairs of QKD nodes. To overcome these problems, in this paper, we present an innovative design—a cluster-based QKD network structure—which is composed of QKD nodes grouped into clusters interconnected by a backbone. A cluster serves as an access network in a master-slave structure to enable effective intra-cluster key agreements. To expand the key distribution over a longer distance and support concurrent key agreements, quantum repeaters are interconnected to form a mesh network as the QKD backbone. In our design, long-range QKD could be achieved by entanglement swapping performed in the backbone network, and the master-slave structure of the clusters is beneficial to the performance of the cluster-based QKD network. The simulation results show that the distance between two neighboring quantum repeaters, the size of quantum memory, quantum memory life-time, the success probability of entanglement distribution, and the success probability of entanglement swapping are essential factors affecting the key generation rate.