UK demonstrates first long-distance quantum-secured link over existing fibre

Raising security but not cost

UK researchers’ work to send quantum-protected data over an existing fibre network challenges assumptions that the tech requires mass infrastructure upgrades.

A UK-led breakthrough could reshape how businesses, governments and telecom providers think about secure communications.

Researchers from the Universities of Bristol and Cambridge have successfully demonstrated the country’s first long-distance quantum-secured communication network.

The team transmitted data over 410km of existing fibreoptic cable between Cambridge and Bristol, using advanced quantum key distribution (QKD) techniques. Unlike traditional encryption methods relying on mathematical complexity, QKD methods are supposedly protected against quantum-based attacks.

The project also tested real-world use cases, including a quantum-secured video call, an encrypted transfer of sensitive health data and secure remote access to a distributed datacentre.

Presented at the 2025 Optical Fiber Communications Conference in San Francisco, the system integrates two QKD methods: one using particles of light to carry encryption keys, and another based on quantum entanglement. It builds on over a decade of work under the UK Quantum Network (UKQN), funded by the Engineering and Physical Sciences Research Council (EPSRC) as part of the Quantum Communications Hub project.

No need for network overhaul

The research challenges assumptions that quantum networks must replace existing systems. Instead, the demonstration shows telecom providers could layer quantum protection onto current broadband services, both raising the bar for cybersecurity and keeping costs manageable.

The demonstration also highlights that such communication can run on today’s fibre networks without needing a complete infrastructure overhaul.

By extension, this could open the door for organisations to adopt quantum-secure systems in the coming years.

“This is a crucial step toward building a quantum-secured future for our communities and society,” said Dr Rui Wang of the University of Bristol.

Co-author Adrian Wonfor, from Cambridge’s Department of Engineering, said the effort “marks the culmination of more than 10 years of work to design and build the UK Quantum Network.”

The UK is not alone in quantum network research. China developed a 4,600-kilometre network linking cities through fibre and satellite in 2021, while researchers in Madrid deployed a nine-node quantum network in 2023.

However, according to a University of Cambridge publication, the UK’s latest milestone stands out because it creates a “long-distance network that can handle both types of QKD, entanglement distribution, and regular data transmission all at once.”

The success of these applications hints at a future where businesses and service providers can operate across networks without fearing high-value data theft.