Round-trip multi-band quantum access network

The quantum network makes use of states to transmit data, which will revolutionize classical communication and allow for some breakthrough applications. Quantum key distribution (QKD) is one prominent application networks, can protect data transmission through mechanics. In this work, we propose an expandable cost-effective access network, in the round-trip structure travel a circle carry information, multi-band technique proposed support multi-user access. Based on realize secure sharing continuous-variable QKD (CV-QKD) protocol. Due encoding characteristics CV-QKD, quadrature components different frequency bands be used information users. feasibility scheme confirmed by comprehensive noise analysis, verified proof-of-principle experiment. results show that each user achieve excess suppression 600 bit/s level generation under 30 km standard fiber transmission. Such networks have ability theoretically could expanded plugging simple modules. Therefore, it paves way near-term large-scale networks.