Field Experimental "Star Type" Metropolitan Quantum Key Distribution Network

TL;DR

This paper reports the first implementation of a trusted-relay-free, star-topology quantum key distribution network covering a metropolis, demonstrating simultaneous multi-user key sharing over existing optical fiber infrastructure.

Contribution

It introduces a novel quantum router enabling full connectivity in a metropolitan QKD network without trusted relays, a significant advancement over prior limited or relay-dependent systems.

Findings

Longest fiber length 42.6 km

Maximum QBER below 8%

Supports simultaneous multi-user key distribution

Abstract

Quantum key distribution (QKD) network has recently attracted growing attentions. Due to the special characteristics of quantum information, to build a full-connectivity QKD network without trusted relays is a stimulating challenge. In this letter, we report on the first realization of QKD network without trusted relays which covers metropolis in the commercial backbone optical fiber networks. The star topology four-user QKD network automatically addresses the quantum signal with a quantum router (QR) and every user in the network can receive and distribute quantum keys to any others simultaneously. The longest and the shortest length of fibers between two geographically separated nodes are 42.6km and 32km respectively, and the maximum average quantum bit error rate (QBER) is below 8%. This result opens a new possibility for the use of QKD into existing network.