Light-powered chip processes information using a quantum 'valley' trick

Researchers have demonstrated a fully integrated chip that uses light, rather than electrons, to carry and process information, an advance they say could point towards faster computers that consume far less energy. The work, led by Monash University in Australia, was published in Nature Photonics.

The chip exploits a quantum property known as the valley degree of freedom, encoding data in the behaviour of light within atomically thin materials patterned with nanoscale structures. Crucially, it works at room temperature, sidestepping the ultra-cold conditions many quantum systems require.

That last point is more than a convenience. A great deal of quantum and advanced photonic research depends on bulky, power-hungry cooling systems that keep components close to absolute zero. A device that performs at room temperature is dramatically easier to imagine outside a specialist laboratory, which is part of why the result has drawn attention.

Everything on a single device

Previous efforts could generate or detect these light-based signals, but not perform both on one piece of hardware. The new device handles the whole chain, creating, directing and reading the information in a single integrated system, and the team showed it could encode and process two separate images at once.

Integrating the full pipeline onto one chip is a significant engineering milestone. In electronics, the move from discrete components to integrated circuits is precisely what made modern computing possible, by shrinking systems, cutting costs and improving reliability. Doing something analogous for valley-based photonics suggests the field is maturing from isolated demonstrations towards usable building blocks.

The ability to handle two images simultaneously hints at the kind of parallelism that makes optical approaches appealing. Light can carry multiple streams of information at once through properties such as wavelength and polarisation, and the valley degree of freedom adds another channel to exploit.

The valley property itself refers to distinct energy states that electrons, and the light coupled to them, can occupy within certain crystal structures. Encoding information in which valley a signal occupies is conceptually similar to using the spin of an electron, an idea that has long tantalised researchers, but doing it with light and at room temperature has proved especially difficult. That the team managed it on a single integrated chip is what sets the work apart.

Why light could beat electrons

Conventional chips move information by pushing electrons through metal wires, a process that generates heat and consumes energy, especially as data is shuttled back and forth. As demand for computing power surges, driven in large part by artificial intelligence, the energy cost of that movement has become a serious constraint on both performance and sustainability.

Photonics offers a potential way around the bottleneck, because light can carry information quickly and with comparatively little heat. The promise is appealing across several domains:

• Faster data movement with lower energy loss than electrical wiring
• Reduced heat generation, easing cooling demands in data centres
• Natural parallelism, with multiple signals carried at once
• Potential applications in artificial intelligence and large-scale data processing
• New approaches to secure communications using light-based encoding

The collaboration spanned institutions in China, Singapore, Germany and Japan, and the researchers see applications ranging from artificial intelligence and advanced data processing to secure communications, where light-based encoding could offer new safeguards.

“What we've built is a complete on-chip system that can create, route and read this information with very high precision.”

— Dr Chi Li, Monash University

Background: the long quest for optical computing

The idea of computing with light is decades old, and optical components are already indispensable in the fibre networks that carry the internet across continents. Where progress has been slower is inside the computer itself, where electronics has remained dominant because it is cheap, mature and easy to miniaturise. Bridging that gap, by making photonic components as compact and manufacturable as their electronic counterparts, has long been the field's central challenge.

Recent interest in atomically thin materials, sometimes called two-dimensional materials, has opened new avenues. These materials exhibit unusual quantum behaviours, including the valley property used here, that researchers are only beginning to harness for information processing. The Monash result is part of a broader wave of work trying to turn those exotic properties into practical technology.

“Demonstrating a full create-route-read chain on one chip is the kind of step that moves a field from physics curiosity towards engineering.”

— Photonics researcher

What happens next

Commercial photonic processors remain some way off, and turning a laboratory demonstration into manufacturable hardware is a notoriously difficult step. The team will need to show the approach can be scaled, fabricated reliably and integrated with existing electronics before it reaches real products. Still, the result adds to growing momentum behind using light to relieve the energy and speed bottlenecks facing conventional electronics, a problem that becomes more pressing with every new wave of computing demand.