Multiuser Differential-Phase-Shift Quantum Key Distribution System on a Ring Network

Quantum key distribution (QKD) has been studied, which is basically a point-to-point system. Therefore, when constructing a QKD network in which any pair of multiple users shares a secret key, full-mesh connections equipping each user with a transmitter and a receiver must be installed. This study presents a QKD system based on the differential-phase-shift QKD protocol, which accommodates multiusers on one transmission line. The proposed system uses a ring network connecting multiple nodes, in which one node is equipped with a transmitter and a receiver and the other nodes are with phase-modulation circuits. The system performance is evaluated and the results indicate that a 100-km ring network can support up to seven nodes.