A research team from the Indian Institute of Technology and Max-Born Institute of Germany have published a study on a novel approach for encoding quantum information: valleytronics.
Aside from their charge, electrons have another parameter that can be manipulated: their “valley pseudospin,” which are the local minima in the energy bands of solids that can be occupied by electrons. By manipulating how many electrons occupies each of the valleys, quantum information can be encoded, processed, and stored at less restrictive temperatures.
The team of scientists say they have achieved a breakthrough in valleytronics that opens up the road to taking quantum computers 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.
The team, led by Associate Professor Gopal Dixit from IIT Bombay, came up with a strategy to break graphene’s valley symmetry using light. Dr. Dixit explains: “By tailoring the polarization of two beams of light according to graphene’s triangular lattice, we found it possible to break the symmetry between two neighboring carbon atoms and exploit the electronic band structure in the regions close to the valleys, inducing valley polarization.” In other words, this enables the use of graphene’s valleys to effectively “write” information.
Dr. Dixit also highlights that 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.
As the poster child of carbon nanomaterials, graphene possesses a plethora of beneficial properties. Pristine graphene has brought many breakthroughs even in conventional electronics. Being able to apply single-layer graphene to quantum computing could change the game.
One of the most attractive aspects of conducting valley operations in graphene is that it’s possible to do so at room temperature. “Our work could open the door to miniature, general-purpose quantum computers that can be used by regular people, much like laptops,” remarks Dr. Dixit.
