Researchers from the University of Bristol and the University of Cambridge have achieved the UK’s first long-distance, ultra-secure data transfer using a quantum communications network. The demonstration included the nation’s first quantum-encrypted video call over a fibre span of more than 410 km between Bristol and Cambridge. The system integrates two types of quantum key distribution (QKD): discrete-variable QKD, which encodes encryption keys into photons, and entanglement-based QKD, where quantum particles are intrinsically linked. The demonstration relied on standard single-mode fibre and coexisted with conventional data traffic, showcasing the feasibility of hybrid classical-quantum networks.
The end-to-end test validated multiple quantum-secure applications, including a live quantum-encrypted video conference, secure transfer of medical data, and quantum-protected access to a remote data center. The trial ran over the UK Quantum Network (UKQN), leveraging four long-distance optical fibre links with three intermediate nodes. The infrastructure uses the EPSRC National Dark Fibre Facility, which provides dedicated research fibre, and integrates low-loss optical switches that enable reconfiguration of both quantum and classical signals. Results were presented at the 2025 Optical Fiber Communications Conference (OFC) in San Francisco.
This marks the first time a long-distance fibre network has successfully combined discrete-variable QKD, entanglement distribution, and secure classical data transmission. The effort is backed by the EPSRC Quantum Communications Hub and supported by industrial partners Toshiba, BT, Adtran, and Cisco. The next phase will be led under the new Integrated Quantum Networks Hub, aiming to develop quantum networking capabilities from local clusters of quantum processors to national and intercontinental-scale networks using low-earth orbit satellites.
Technical Highlights:
- 410 km quantum-secure data transfer between Bristol and Cambridge via standard single-mode fibre
- Integration of two quantum key distribution (QKD) techniques:
- Discrete-variable QKD (photon-based encryption)
- Entanglement-based QKD (quantum correlation between particles)
- Applications tested:
- Quantum-encrypted video call
- Transfer of encrypted medical data
- Remote access to distributed data centre
- Network infrastructure:
- 4 fibre links + 3 intermediate nodes on the EPSRC National Dark Fibre Facility
- Low-loss optical switches for signal path reconfiguration
- Coexistence of quantum and classical data traffic
- Results presented at OFC 2025, San Francisco
“This is a crucial step toward building a quantum-secured future for our communities and society. More importantly, it lays the foundation for a large-scale quantum internet—connecting quantum nodes and devices through entanglement and teleportation on a global scale.”
— Dr Rui Wang, Lecturer for Future Optical Networks, University of Bristol
Addendum: UK Integrated Quantum Networks Hub
The Integrated Quantum Networks Hub (IQN Hub) is the UK’s flagship initiative to develop scalable quantum networking infrastructure, supporting secure communications, distributed quantum computing, and sensing across local, national, and intercontinental distances. Launched under the UK National Quantum Technologies Programme, the Hub is funded by the Engineering and Physical Sciences Research Council (EPSRC) and UK Research and Innovation (UKRI), building on over a decade of work through the earlier Quantum Communications Hub.
The mission of the IQN Hub is to integrate all major quantum networking technologies—including entanglement distribution, quantum key distribution (QKD), quantum repeaters, and classical control protocols—into a cohesive framework capable of supporting a future quantum internet. It aims to interconnect quantum processors, enable secure data links immune to quantum attacks, and support global-scale entangled networks using fibre and satellite channels.
The IQN Hub brings together a consortium of leading academic institutions and industry stakeholders. Core participants include:
- Heriot-Watt University (lead institution)
- University of Cambridge
- University of Bristol
- University of York
- Toshiba Research Europe
- BT, Adtran, and Cisco
Key Milestones to Date:
- 2015–2020: UKQN South metro network deployed between Cambridge, BT Labs, and Adastral Park
- 2020: Bristol multi-user entanglement-sharing network demonstrated
- 2022: Launch of UKQN backbone across 410 km with intermediate nodes
- 2024: Field trials integrating discrete-variable and entanglement-based QKD over long distances
- 2025: First long-distance quantum-secure video call and data transmission over the integrated UKQN
The Hub will next pursue cross-layer protocol development, hybrid classical-quantum network management systems, and field trials that extend quantum-secured communications over satellite-to-ground links and intercontinental fibre routes.
