• Researches use pristine graphene to encode, process and store quantum information via valleytronics.
• Quatum computers owned by Google, IBM and Microsoft have to be kept at ultra-low temperatures below -196.1°C, which makes them costly and impractical to operate.
• Valleytronics at petahertz rates is possible, which exceeds modern computational speeds by a million times.

Researchers from the Indian Institute of Technology (IIT) Bombay have found a way to use pristine graphene for encoding, processing and storing quantum information that can operate at room temperature. 

Quantum computers such as those at Google, IBM, or Microsoft are large, complex, and expensive and can only operate at ultra-low temperatures of nearly –200°C, thus making them very impractical for use on a large scale.

Quantum computers have recently become a hot-button topic because of their theoretical potential to outperform conventional computers by several orders of magnitude in terms of speed.

A quantum computer can achieve these feats because it encodes information in quantum bits rather than the binary “0” or “1” that regular electronics use. Quantum bits are superpositions of “0” and “1”, and can therefore take intermediate values, making computations much faster.

Sadly, such quantum computation is not yet possible at room temperature; and existing computers, such as those owned by Google, IBM, and Microsoft, have to be kept at ultra-low temperatures below -196.1°C, which makes them costly and impractical to operate.

A team of scientists from the Indian Institute of Technology (IIT) Bombay, and Max-Born Institut, Germany, have achieved a breakthrough in “valleytronics” that opens up the road to taking quantum computers all the way to room temperature operation.

Their findings, published in Optica, describe a way to perform valley operations in single-layer (one atom thick) or pristine graphene (carbon atoms arranged in a hexagonal sheet structure), which was hitherto assumed to be impossible — atomically thin layers of graphene have electron valleys but, due to the material’s inherent symmetry, they were deemed useless for valley operations. 

Way to household quantum computers?

Aside from their charge, electrons have another parameter that can be manipulated: their “valley pseudospin,” which is the local minima in the energy bands of solids that can be occupied by electrons. By manipulating how many electrons occupy each of the valleys, quantum information can be encoded, processed, and stored at less restrictive temperatures. 

Led by Associate Professor Gopal Dixit from IIT Bombay, the team came up with a strategy to break graphene’s valley symmetry using light.

“By tailoring the polarisation of two beams of light according to graphene’s triangular lattice, we found it possible to break the symmetry between two neighbouring carbon atoms and exploit the electronic band structure in the regions close to the valleys, inducing valley polarisation,” he said.

In other words, this enables the use of graphene’s valleys to effectively “write” information. 

Dixit said the flashes of light can cause electrons to wiggle several hundred trillion times a second.

“In theory, this means valleytronics at petahertz rates is possible, which exceeds modern computational speeds by a million times. Our work could open the door to miniature, general-purpose quantum computers that can be used by regular people, much like laptops,” he said. 

Soon, quantum computers will cease to be a thing of wonder residing in large labs and have a place in the everyday household.