Quantum Internet still looks like science fiction from the future, but at the same time, an important step has been taken towards it and scientists from Edinburgh have made it happen.
Physicists from Heriot-Watt University announced a quantum network prototype that combines two smaller networks into an eight-user, reconfigurable system capable of routing and even teleporting quantum entanglement on demand. Details of the experiment are presented in the journal Natural photonics.
Professor Mehul Malik, who led the research, said: “There have been demonstrations where, in a single quantum network, entanglement is distributed among multiple users. However, for the first time we were able to connect two independent networks. This is not just a new way to distribute entanglement – we have enabled direct communication between networks. This is an important milestone on the path to creating a full-fledged quantum Internet.”
The chaos of light as a resource
The prototype built in his lab is based not on a shiny quantum chip or a bespoke device but on a regular store-bought fiber optic cable that costs less than £100.
The team used the light scattering effect in optical fibers to create a reconfigurable entanglement router based on it.
“Light in the fiber reflects chaotically in hundreds of directions. But we were able to exploit this chaos and turn it into a valuable resource,” explains lead author Natalia Herrera Valencia.
The result is a reprogrammable multi-port device that can distribute quantum entanglement among users in different fashions, with the ability to switch between local, global, and hybrid connectivity configurations.
The advantage of the system is its multiplexing capability, meaning it can serve multiple users at the same time, instead of a pair at a time. Multiplexing allows classical telecommunications networks to transmit huge amounts of data over a single fiber at different wavelengths; Here a similar principle applies in the quantum regime.
The most impressive achievement is the multi-channel teleportation of entanglement – the exchange of it between four remote users over two channels at the same time. Previous tests have demonstrated teleportation using entanglement, but not for multiple simultaneous users in such a flexible architecture.
“By shaping the light wavefront at the input, we are essentially programming the fiber, turning the chaotic scattering within it into a powerful multidimensional optical circuit. This allows us to steer quantum entanglement wherever we need it – and even teleport it – using this seemingly ordinary piece of cable,” said Herrera Valencia.
Breakthrough for quantum computing
Professor Malik is sure that this experiment is a breakthrough not only in quantum communication but also in computing.
“The prospects are huge. Quantum computing has the potential to change the world, revolutionize drug discovery and development, create new battery materials and greatly enhance machine learning capabilities. One of the most promising ways to create large-scale quantum computers is to network many small quantum processors. Our prototype is just a network through which many users, i.e. similar processors, can distribute and exchange entanglement. This could be exactly the breakthrough the entire industry has been waiting for. Yes, this is just a lab demonstration for now, but the principle itself is scalable,” he concluded.
