Professor Cristian Bonato, co-lead of Heriot-Watt’s Quantum Photonics Laboratory, has worked with colleagues across both Heriot-Watt and Europe on what’s been cited as a new breakthrough.

At present, quantum networks rely on expensive lasers and additional equipment to make single atoms ‘talk’ to each other using light—a crucial requirement for quantum communication to work, and one which ensures all communication remains secure.

Bonato and the team have developed a semiconductor system with single atoms that automatically all emit light at the same frequency, removing the need for additional scientific and technological equipment, as well as reducing significant costs.

Professor Cristian Bonato explained: “Semiconductors are very appealing for quantum communications. They use chips similar to those we find in mobile phones and computers, which means we already have the manufacturing capability in place.

“Small-scale variations in the semiconductor mean the atoms all emit light at slightly different frequencies.

“This is a big issue for quantum communication since it means the atoms cannot talk to each other—it’s like having your radio receiver tuned at a different frequency than the transmitter: no signal reception is possible.

“Until now, this problem has been solved by using extra lasers and complex frequency-conversion equipment, which is very expensive and makes quantum a less attractive proposition.”

Bonato and the researchers decided to add vanadium atoms to the semiconductor. Vanadium is mostly used to make extremely strong steel alloys, for use in tools or armour plating.

They chose to experiment with vanadium because it emits light at a frequency compatible with standard telecommunication fibre networks. This removes the need for new fibre to be laid down, which could be a major expense for any organisation looking to move to quantum networking.

The scientists implanted single vanadium atoms into silicon carbide, a semiconductor comprising a lattice of silicon and carbon atoms.

As Bonato explained: “Each vanadium atom acts like a tiny antenna, which emits light at a given frequency.

“This antenna can perturb when heavier atoms are sitting nearby. For example, in nature, some silicon atoms are heavier than normal, as they host an additional neutron.

“A heavier atom nearby compresses the antenna, making it emit light at a slightly different frequency. We solved this problem by growing our semiconductor using identical silicon and carbon atoms.”

Bonato says the finding heralds a breakthrough in quantum communications.

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“We now have a network of single atoms all operating at exactly the same optical frequency, in the telecommunication range,” Bonato continued. “Therefore these atoms can now talk to each other and transmit quantum information.

“Using silicon carbide was intentional. It’s widely used in the electric vehicle industry, so there are already standard manufacturing processes and knowledge of the material in place – that’s a huge saving on investment, compared to using a novel material.

“Data is the new currency and we need quantum networks to keep it secure. Our breakthrough will help accelerate the adoption of quantum networks and increase the security of our communications.”

Bonato worked with colleagues at Heriot-Watt University and collaborators in Germany, Austria and Sweden on the research, which was funded by the European Commission and the UK Engineering and Physical Sciences Research Council (EPSRC).

The findings of the research has been reported in Nature Communications.