A Novel Setup To Carry Out Quantum Information Processing At Room Temperatures

A team of researchers from the Indian Institute of Technology, Bombay (IITB) has recently proposed a new approach for quantum information processing at room temperature. This approach uses a stack of specially designed layered materials.

The research recently appeared in journal Physical Review B and was funded by the Department of Science and Technology, India (DST).

Let us see some background about quantum computers to understand the current work.

We all know that quantum computers can revolutionize computing. Not only can they make computation faster, but also offer solutions that modern computers are simply incapable of, such as in the field of secure encryption and decryption of information. But a major problem is that to have stable quantum information processing, we need temperature close to -273 ºC.

Unlike normal bits which have 0’s or 1’s, quantum computers use different computing blocks known as qubits. One of the possibilities of realizing qubits is through valley materials. For qubits to be possible, its states need to have a linear superposition or have ‘coherence’ which degrades with time and is more likely at higher ambient temperatures. This is the cha

What are valley materials?
This is a type of material whose group of energies are such that electrons in the material can occupy, take the shape of valleys. The two opposite varieties of valleys make up the two states in a qubit.

In the current work, the researchers theoretically created two setups for wherein it is possible to maintain the quantum coherence even at room temperatures. They chose two varieties of graphene as valley materials in these setups. The two proposed implementations are one, using anisotropic plasmons in phosphorene and second with hyperbolic phonon polaritons in α−MoO3.

The valley materials were stacked on top of other materials that are responsible for creating coherent superposition of particles, called ‘excitons’, in valley states. Without these materials, the excitons would not reside in the valley states.

“Composed of atomically thin materials stacked on top of each other, the entire device is less than a hundred nanometers thick,” says Prof Anshuman Kumar, who heads the Laboratory of Optics of Quantum Materials at IIT Bombay and is one of the co-authors of the study. “That makes it a thousand times thinner than a human hair.“

Next, the team added electrostatic voltages across the theoretical setups and determined the coherence of the valley states through numerical calculations. They concluded that both setups could support coherent valley states even at room temperatures. These states could thus be the fundamental building blocks of quantum information or qubits.

Moreover, the thickness of the materials and the electrostatic voltage could also be used to tune the degree of coherence at different temperatures.

“The tunability of the quantum states via electrostatic voltages makes it possible to turn them into technological reality,” remarks Prof Kumar, highlighting their importance in making this theory practical. However, he says that there are challenges ahead “The setup requires the materials to be very pure, and at the nanometres scale, this is challenging to achieve.”

Although the large-scale manufacturing of the valley materials is possible in the next few years, achieving the uniformity of materials so thin might take a while longer.

Journal Reference:
Engineering valley quantum interference in anisotropic van der Waals heterostructures (Phy. Rev. B) DOI: doi.org/10.1103/PhysRevB.102.045416