Heriot-Watt Team Routes Entanglement via Ordinary Optical Fibres

By LiFi Tech News Team

In a significant leap forward for scalable quantum communications, physicists in the UK have successfully routed and teleported entangled states of light between two four-user quantum networks. This milestone, achieved by a team at Heriot-Watt University in Edinburgh, promises to overcome some of the most persistent hurdles in building the quantum internet of the future.

Led by Mehul Malik and Natalia Herrera Valencia, the researchers employed a radical new method that uses light-scattering processes within commercially available optical fibres to program a circuit. This innovation steers away from conventional methods based on photonic chips, offering a more scalable and robust alternative that integrates naturally with existing infrastructure.

Harnessing Chaos: A New Approach to Optical Circuits

The experiment used multi-mode optical fibres, which typically scatter light via random linear optical processes. In these structures, light tends to ricochet chaotically through hundreds of internal pathways—a phenomenon that usually scrambles entanglement.

However, building on previous findings from the Institut Langevin in Paris, the Heriot-Watt team knew that this scrambling could be calculated by analysing how the fibre transmits light. By harnessing these scattering processes, they successfully turned the medium into a programmable entanglement router.

“The main challenge was the learning curve and understanding how to control quantum states of light inside such a complex medium,” said Natalia Herrera Valencia. “It took time and iteration, but we now have the precise and reconfigurable control required for reliable entanglement distribution.”

The "Top-Down" Advantage

The team describes their methodology as a “top-down” approach. By separating the layer where light is controlled from the layer where it is mixed, the architecture is simplified, and optical losses are significantly reduced.

The resulting reconfigurable multi-port device can distribute quantum entanglement among multiple users simultaneously in various patterns. It can switch between local and global connections on demand, offering a flexibility that traditional photonic chips struggle to match.

Furthermore, this waveguide-based approach supports multiplexing, allowing multiple quantum processors to access the system simultaneously. This mimics the efficiency of classical telecommunications networks, where huge amounts of data are sent through a single fibre using different wavelengths of light.

Scalability and Future Applications

Current photonics chip technologies face difficulties in scaling up and are highly sensitive to manufacturing imperfections. In contrast, Malik notes that their new approach “opens up access to a large number of modes, providing significant improvements in terms of achievable circuit size, quality, and loss.”

The implications of this technology extend far beyond networking. The team suggests that these large-scale photonic circuits could find applications in machine learning and quantum computing.

Correlations with LiFi Technology

While this breakthrough focuses on guided light within optical fibres, the underlying physics holds intriguing parallels for Light Fidelity (LiFi) technology. LiFi systems, which transmit data wirelessly through light, often contend with similar challenges regarding light scattering and multipath interference, light bouncing off walls and objects in a room.

The Heriot-Watt team’s success in calculating and harnessing chaotic scattering patterns to program circuits could offer a roadmap for next-generation LiFi systems. By understanding how to control light in a complex, scattering medium, future LiFi networks might use environmental reflections not as noise, but as additional programmable channels for data transmission.

Furthermore, as the industry moves toward "Quantum LiFi", wireless optical networks capable of Quantum Key Distribution (QKD), robust fibre-based quantum routers will be essential. This new technology could serve as the secure backbone that feeds entangled states into wireless LiFi access points, enabling a seamless, end-to-end quantum communication infrastructure from the core network to the wireless edge.

Looking Ahead

The researchers, whose work has been published in Nature Photonics, aim to explore larger-scale circuits capable of operating on more photons. Commercialisation is also on the horizon, with Herrera Valencia leading efforts to take this network technology out of the laboratory and into the real world.

For the quantum communications industry, and the broader optical communication sector, including LiFi developers, this development marks a pivotal moment, proving that the chaotic nature of light can be tamed to build the networks of tomorrow.

Source: https://physicsworld.com/a/quantum-photonics-network-passes-a-scaling-up-milestone/