A Three-Node QKD Network Based on a Two-Way QKD System

We demonstrate a three-node active quantum key distribution (QKD) network with our previous two-way QKD system. An optical switch is used as a router to connect the two nodes. Adjacent nodes are connected by a 25 km optical fiber. The test over 11 h shows that our system can reduce the Raleigh backscattering efficiently in the absence of the storage fiber. Furthermore, the obtained average sifted key is about 1.2 kbps in the network, with high visibility and low quantum bit error rate in the long-time test.