Scientists compute with light inside hair-thin optical fiber

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 superfast quantum computers and unhackable communications networks.

Professor Mehul Malik of Heriot-Watt's School of Engineering and Physical Sciences says, "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." Malik is an experimental physicist.

However, the complexity and size of optical circuits make them more difficult to manufacture and operate, which may have an impact on their performance. Our work demonstrates a different—and more flexible—method of creating optical circuits by utilizing a naturally occurring mechanism."

The research was carried out by Professor Malik and his colleagues utilizing commercial optical fibers, which are often used globally to provide the internet to our homes and offices. These fibers use light to transmit data; they are thinner than a human hair's thickness.

They discovered that they could precisely design optical circuits within an optical fiber by taking use of the light's inherent scattering characteristic.

Today, the study appears in the journal Nature Physics.

Professor Malik says, "Light gets scattered and mixed in complex ways when it enters an optical fiber." "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."

Future quantum technologies, which are created on a small 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 computing capacity.

"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," says Professor Malik. "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 medication discovery, climate prediction, and space exploration are anticipated to be made possible by quantum computers. Optical circuits are also employed in machine learning, or artificial intelligence, to handle enormous amounts of data rapidly.

According to Professor Malik, light's multidimensionality is what gives it strength.

"We can encode a lot of information on a single particle of light," he said. Regarding its temporal organization, spatial structure, and color. And a tremendous amount of processing power can be unlocked if you can compute with all of those qualities simultaneously."

The researchers also demonstrated how quantum entanglement—the phenomenon where two or more quantum particles, like light photons, stay linked even when they are separated by enormous distances—can be controlled using their programmable optical circuits. Many quantum technologies, including error correction within a quantum computer and the most secure forms of quantum encryption, depend on entanglement.

Together with academic partners from Lund University in Sweden, Sapienza University of Rome in Italy, and the University of Twente in the Netherlands, Professor Malik and his research team at the Beyond Binary Quantum Information Lab at Heriot-Watt University undertook the study.