For decades, physicists have dreamed of a quantum internet: a planetary web of ultrasecure communications and super-powered computation built not from electrical signals, but from the ghostly connections between particles of light.

Now, Heriot-Watt scientists say they’ve taken a major step towards turning that vision into something real.

Researchers from the School of Engineering and Physical Sciences have unveiled a prototype quantum network that links two smaller networks into one reconfigurable, eight-user system capable of routing and even teleporting entanglement on demand.

The demonstration, reported this week in Nature Photonics, sets a new benchmark for how large, flexible and capable quantum networks can become.

Professor Mehul Malik said: “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.

“This is a major milestone on the road to a real-world quantum internet.”

Using light’s chaos as a resource

At the heart of the Heriot-Watt prototype, instead of a gleaming quantum chip or custom-engineered device, is a shop-bought optical fibre that costs less than £100.

The team harnessed the scattering behaviour of light inside an optical fibre to programme their reconfigurable entanglement router.

Dr Natalia Herrera Valencia, lead author of the study, said, “Light tends to ricochet chaotically through the fibres’ hundreds of internal pathways. We turned that chaos into a resource.

The result is a reconfigurable multi-port device that can distribute quantum entanglement between users in multiple patterns, switching between local connections, global connections and mixed configurations at will.

Crucially, the system can multiplex these channels, meaning it can serve many users simultaneously, rather than one pair at a time. Multiplexing is what allows classical telecoms networks to send vast amounts of data down a single fibre using different wavelengths; here, a similar concept is deployed in the quantum regime.

Most strikingly, the team achieved multiplexed entanglement teleportation, swapping entanglement between four distant users across two channels at once. Previous demonstrations have teleported entanglement, but not across so many simultaneous users in such a flexible architecture.

Dr Natalia Herrera Valencia said: “By shaping the light at the input, we effectively programmed the fibre, transforming its messy internal scattering into a powerful, high-dimensional optical circuit.”

“That lets us route quantum entanglement wherever we want, even teleport it, using this deceptively simple piece of fibre.”

A leap for quantum computing

Professor Malik says the demonstration has exciting implications for quantum computing.

“It’s really exciting. Quantum computing could be world-changing, transforming how we find and develop medicines, create new materials for batteries and supercharge machine learning.

“A promising current approach to building a large-scale, powerful quantum computer is to interconnect lots of 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.

“Yes, this is a lab-scale demonstration, but the principle is extendable.”

The work is part of the UK’s £22m Integrated Quantum Networks (IQN) Hub, which aims to build the country’s first large-scale quantum network and help meet the government’s mission to deploy the world’s most advanced quantum network by 2035.

The research team is part of a major research and technology development consortium, the £22M Integrated Quantum Networks (IQN) Hub. Led by Heriot-Watt University, the project is funded by the Engineering and Physical Sciences Research Council (EPSRC) and brings together the expertise of 14 leading UK universities plus over 50 industrial partners to secure the UK’s leadership in quantum networking. The Hub’s vision aligns with one of the UK Government’s national quantum strategic missions, for the UK to have deployed the world’s most advanced quantum network, at scale, by 2035. This research was supported by the UK Engineering and Physical Sciences Research Council (EPSRC), the European Research Council (ERC), and the Royal Academy of Engineering. The work was carried out by Heriot-Watt University’s Beyond Binary Quantum Information Lab in collaboration with the Edinburgh Mostly Quantum Lab.