Multi-node quantum key distribution network using existing underground optical fibre infrastructure

TL;DR

This paper demonstrates a multi-node quantum key distribution network in Cyprus using existing underground optical fibre infrastructure, showing reliable, high-rate quantum communication suitable for secure critical applications.

Contribution

It is the first deployment of a multi-node QKD network over existing commercial underground fibre, integrating wavelength multiplexing and ring architecture for efficient, scalable quantum communication.

Findings

Consistent key generation rates across all nodes

Reliable operation in a real-world environment

Feasibility of using existing telecom infrastructure for quantum security

Abstract

Quantum key distribution (QKD) offers unconditional information security by allowing two distant users to establish a common encryption key resilient to hacking. Resultingly, QKD networks interconnecting critical infrastructure and enabling the secure exchange of classified information, can provide a solution to the increasing number of successful cyberattacks. To efficiently deploy quantum networks, the technology must be integrated over existing communication infrastructure, such as optical fibre links. Yet, QKD poses stringent requirements on the conditions of the network over which it is deployed. This work demonstrates the first quantum communication network in Cyprus via the deployment of a multi-node quantum network, exploiting existing commercial underground optical fibre. The network employs bidirectional occupation of fibres and wavelength multiplexing in a ring architecture to achieve, with minimal use of dark fibres, high-rate QKD. Results obtained reveal consistent key generation rates across all nodes, confirming reliable operation in a real-world environment. This deployment highlights the feasibility of leveraging existing telecom infrastructure for quantum-secured communication, marking a significant step toward scalable and cost-effective quantum networks suited for critical applications.