Implementation of a 46-node quantum metropolitan area network

TLDR

Quantum key distribution enables secure key exchanges and, supported by field tests, demonstrates the feasibility of building a global quantum network. The study aims to show that a practical quantum network can be built by overcoming challenges such as scalable topologies, simple maintenance, extendable configuration, and node‑failure robustness, as demonstrated by a 46‑node metropolitan‑area network. The network was operated for 31 months using standard maintenance equipment, an extendable configuration, diverse topologies, and a sophisticated key‑control centre for QKD pairing and key management. The 46‑node network enabled simultaneous secure audio calls for 11 user pairs using one‑time pad encryption, and its integration with intercity backbones and satellite links demonstrates a path toward a global quantum network.

Abstract

Abstract Quantum key distribution (QKD) enables secure key exchanges between two remote users. The ultimate goal of secure communication is to establish a global quantum network. The existing field tests suggest that quantum networks are feasible. To achieve a practical quantum network, we need to overcome several challenges including realizing versatile topologies for large scales, simple network maintenance, extendable configuration and robustness to node failures. To this end, we present a field operation of a quantum metropolitan-area network with 46 nodes and show that all these challenges can be overcome with cutting-edge quantum technologies. In particular, we realize different topological structures and continuously run the network for 31 months, by employing standard equipment for network maintenance with an extendable configuration. We realize QKD pairing and key management with a sophisticated key control centre. In this implementation, the final keys have been used for secure communication such as real-time voice telephone, text messaging and file transmission with one-time pad encryption, which can support 11 pairs of users to make audio calls simultaneously. Combined with intercity quantum backbone and ground–satellite links, our metropolitan implementation paves the way toward a global quantum network.