Programmable photonic circuits in optical fibres
Image credit: Heriot-Watt University
Scientists at Heriot-Watt University have reported a new way to programme optical circuits, which are critical to future technologies such as hack-proof communications networks and ultrafast quantum computers. The research has been published in the journal Nature Physics.
“Light can carry a lot of information, and optical circuits that compute with light – instead of electricity – are seen as the next big leap in computing technology,” explains Mehul Malik, an experimental physicist and professor of physics at Heriot-Watt’s School of Engineering and Physical Sciences.
“But as optical circuits get bigger and more complex, they’re harder to control and make – and this can affect their performance. Our research shows an alternative – and more versatile – way of engineering optical circuits, using a process that occurs naturally in nature.”
Malik and his team conducted their research using commercial optical fibres that are thinner than the width of a human hair and use light to carry data. By harnessing the natural scattering behaviour of light inside an optical fibre, they found they could programme optical circuits inside the fibre in highly precise ways.
“When light enters an optical fibre, it gets scattered and mixed in complex ways,” Malik says. “By learning this complex process and precisely shaping the light that enters the optical fibre, we’ve found a way to carefully engineer a circuit for light inside this disorder.”
Optical circuits are critical to the development of future quantum technologies, which are engineered on a microscopic level by working with individual atoms or photons. These technologies include powerful quantum computers with immense processing power and quantum communications networks that can’t be hacked.
“Optical circuits are needed at the end of quantum communications networks, for example, so the information can be measured after it’s travelled long distances,” Malik explains. “They are also a key part of a quantum computer, where they are used for performing complex calculations with particles of light.”
Quantum computers are expected to unlock big advances in areas including drug development, climate prediction and space exploration. Machine learning and AI is another area where optical circuits are used to process vast volumes of data very quickly.
Professor Malik says the power of light was in its multiple dimensions.
“We can encode a lot of information on a single particle of light,” he adds. “On its spatial structure, on its temporal structure, on its colour. And if you can compute with all of those properties at once, that unlocks a massive amount of processing power.”
The researchers also showed how their programmable optical circuits can be used to manipulate quantum entanglement, a phenomenon when two or more quantum particles – such as photons of light – remain connected even when they’re separated by vast distances. Entanglement plays an important role in many quantum technologies, such as correcting errors inside a quantum computer and enabling the most secure types of quantum encryption.
Malik and his research team in the Beyond Binary Quantum Information Lab at Heriot-Watt University conducted the research with partner academics from institutions including Lund University in Sweden, Sapienza University of Rome in Italy and the University of Twente in the Netherlands.
