Scientists in Edinburgh have taken a significant step towards a viable quantum internet by linking two separate quantum networks together for the first time using standard, commercially available optical fibre.
Researchers at Heriot-Watt University unveiled a prototype that connects two smaller networks into a single, reconfigurable eight-user system capable of routing and teleporting quantum entanglement on demand.
The demonstration, detailed in Nature Photonics, sets a new benchmark for the flexibility and capability of future quantum networks, which promise ultrasecure communications and powerful distributed computation.
Instead of relying on expensive, custom-engineered quantum chips, the Heriot-Watt prototype uses a standard multimode optical fibre that costs less than £100. The team harnessed the usually chaotic scattering behaviour of light inside the fibre to turn it into a programmable entanglement router.
“This is a major milestone on the road to a real-world quantum internet,” said Professor Mehul Malik from Heriot-Watt’s School of Engineering and Physical Sciences.
“Other teams had already demonstrated that you can build a single quantum network and send entanglement to many users at once. But this is the first time anyone has managed to link two separate networks together. It doesn’t just distribute entanglement in different ways, it actually lets one network talk to the other.”
Chaos becomes a resource
Dr Natalia Herrera Valencia, lead author of the study, explained that light tends to “ricochet chaotically” through the fibre’s internal pathways. By shaping the light at the input, the team turned that chaos into a resource, transforming the fibre into a high-dimensional optical circuit that can be programmed to route entanglement.
Crucially, the system can multiplex these channels, serving many users simultaneously rather than one pair at a time. The team achieved multiplexed entanglement teleportation, swapping entanglement between four distant users across two channels at once.
Professor Malik noted that the demonstration has exciting implications for scaling up quantum computing, as a promising approach to building large-scale machinery involves interconnecting many smaller quantum processors.
“Our prototype is a network that can flexibly distribute and swap entanglement among many users, or quantum processors – it could be the breakthrough quantum computing has been waiting for,” Malik said.
The work is part of the UK’s £22m Integrated Quantum Networks (IQN) Hub, which aims to help meet the government’s mission to deploy the world’s most advanced quantum network by 2035.
