An international team of researchers based in Brisbane and France have developed a single photon source a million times smaller and 20 times brighter than existing sources. Their results were published today in Nature Photonics.
“I was, and still am, amazed by the quality of the source we obtained,” says Professor Pascale Senellart, team leader at the Centre National de la Recherche Scientifique in Paris. “I never thought it would be that good!”
Photonics is the technology that drives the internet, using pulses of light through fiber optic cables to transmit information.
An especially powerful version of this tech is quantum photonics, which uses single photons – the most basic unit of light. Quantum photonics could enable equipment used in our communications networks, measurement tools, and computation.
Scientists have been exploring ideas for future quantum technologies for decades, but until now the difficulty of generating single photons prevented these theories from becoming reality – to get even one photon you had to use bulky, inefficient, and extremely expensive equipment.
With “even a small handful of 10 to 20 single photons, you could do things that exceed the computational capabilities of modern computing,” says Professor Andrew White from the University of Queensland.
“The last missing piece of the puzzle was the photon sources. We didn’t have a scalable technology, and it was a real roadblock,” says White.
A bright new light
The new photon sources are tiny, and use a structure and technology very close to those used in LEDs.
In contrast to previous photon sources, which White says only worked “one time in a million,” the new sources work 80% of the time, and produce near-perfect quality photons.
The team uses semiconductor quantum dots – a kind of artificial, engineered atom – to generate quantum light. Miniscule cavities etched around these quantum dots control where the photons come out. This makes the source much brighter, as the light is emitted in one direction, unlike natural light sources, which are emitted in all directions.
Associate Professor Brant Gibson from RMIT, who was not involved in the research, says the results are “very impressive”, and open the door to new technologies.
“This technological advance has the potential for ultra high-speed quantum photonic networks to become a reality,” he says.
Into the future
“Applications relying on single photons are not in the general public’s world yet,” says Pascale Senellart. “Here we are developing the future of communication, sensing and computing technologies.”
“This won’t be in your iPhone any time soon,” agrees White. “But it will change important things.”
Quantum photonics has been implicated in quantum voting protocols – a way to prevent vote rigging – and highly secure communications, such as quantum cryptography and quantum key distribution, which could lead to unimpeachable security systems.
“Another end goal is the ‘famous’ quantum computer, that could in principle surpass any processing capabilities that one can envisage with current technologies,” says Senellart.
Other research groups are now keen to work with the new devices, which White’s team at the Centre for Engineered Quantum Systems are scaling up and using in complex simulations.
“[There] is nothing so rewarding, when you have worked hard on an extremely ambitious and exploratory technology, to see that people are just waiting for your devices,” says Senellart.
“We cannot wait to test these new ideas and see how far our technology can go.”