Researchers at Edinburgh, Scotland's Heriot-Watt University have developed a potent new method for programming optical circuits, which are essential for the development of future technologies like ultrafast quantum computers and unhackable communications networks.
Light traveling through an optical fiber sitting on top of a conventional electronic circuit board. Image Credit: Heriot-Watt University
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.
Mehul Malik, Experimental Physicist, School of Engineering and Physical Sciences, Heriot-Watt University
Malik says, “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.”
The research was carried out by Professor Malik and colleagues using commercial optical fibers, which are commonly used globally to deliver the Internet to homes and offices. These fibers use light to transmit data; the fibers are thinner than a human hair’s thickness.
The scientists discovered that they could precisely program optical circuits inside an optical fiber by taking advantage of the light’s inherent scattering behavior.
The research is published in the journal Nature Physics.
When light enters an optical fiber, it gets scattered and mixed in complex ways. By learning this complex process and precisely shaping the light that enters the optical fiber, we’ve found a way to carefully engineer a circuit for light inside this disorder.
Mehul Malik, Experimental Physicist, School of Engineering and Physical Sciences, Heriot-Watt University
Future quantum technologies, which are created on a microscopic scale by interacting with individual atoms or photons, or particles of light, depend heavily on optical circuits. These technologies include unhackable quantum communications networks and potent quantum computers with enormous processing power.
Malik explains, “Optical circuits are needed at the end of quantum communications networks, for example, so the information can be measured after it’s traveled long distances. They are also a key part of a quantum computer, where they are used for performing complex calculations with particles of light.”
Large-scale advancements in fields like drug development, climate prediction, and space exploration are anticipated to be made possible by quantum computers. Optical circuits are also used in machine learning, or artificial intelligence, to process enormous amounts of data rapidly.
Professor Malik said the power of light was in its multiple dimensions.
Malik continues, “We can encode a lot of information on a single particle of light. On its spatial structure, on its temporal structure, on its color. And if you can compute with all of those properties at once, that unlocks a massive amount of processing power.”
The researchers also demonstrated how quantum entanglement - the phenomenon where two or more quantum particles, like light photons, stay connected even when they are separated by enormous distances - can be controlled using programmable optical circuits. Many quantum technologies, including error correction within a quantum computer and the most secure forms of quantum encryption, depend on entanglement.
Professor Malik and the 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.
Journal Reference
Goel, S., et al. (2024) Inverse design of high-dimensional quantum optical circuits in a complex medium. Nature Physics. doi.org/10.1038/s41567-023-02319-6.