Apr 25 2019
For several years, scientists have been making efforts to develop a quantum computer that could be scaled up by the industry. However, qubits—the basic elements of quantum computing—are still not sound enough to deal with the noisy environment presented by a quantum computer.
Quantum Computers" />Researchers at various Microsoft Quantum lab sites, including the lab of Michael Manfra at Purdue University, collaborated to create a device that could bring more scalable quantum bits. Pictured here are Purdue researchers Candice Thomas (left) and Geoff Gardner. (Image credit: Microsoft Station Q Purdue photo)
In a theory put forward just two years ago, a technique has been proposed to render qubits more resilient by combining indium arsenide, a semiconductor, with aluminum, a superconductor, into a planar device. Currently, this theory has received experimental support for a device that could also help the qubits to be scaled up.
A state of “topological superconductivity” is created by this semiconductor-superconductor combination, thereby possibly protecting against even trivial variations in the environment of a qubit that interfere with its quantum nature—a well-known challenge termed “decoherence.”
Due to the flat “planar” surface of the device, it is potentially scalable. This platform is already being employed in the industry in the form of silicon wafers to develop classical microprocessors.
The study has been reported in Nature and has been headed by the Microsoft Quantum lab at the University of Copenhagen’s Niels Bohr Institute, which created and measured the device. The semiconductor-superconductor heterostructure was fabricated by the Microsoft Quantum lab at Purdue University with the help of a method known as molecular beam epitaxy, and the initial characterization measurements were also carried out there.
Also part of the study were theorists from Station Q, a Microsoft Research lab in Santa Barbara, California, together with the University of Chicago and the Weizmann Institute of Science in Israel.
Because planar semiconductor device technology has been so successful in classical hardware, several approaches for scaling up a quantum computer having been building on it.
Michael Manfra, Bill and Dee O’Brien Chair Professor of Physics and Astronomy, Purdue University
Manfra is also a professor of electrical and computer engineering and materials engineering, and leads Purdue’s Microsoft Station Q site.
These experiments offer proof of the fact that when indium arsenide and aluminum are brought together to create a device known as a Josephson junction, they can support Majorana zero modes, which have been predicted by researchers to have topological protection against decoherence.
It has also been found that indium arsenide and aluminum work well in tandem since a supercurrent flows well between them. This is due to the fact that in contrast to a majority of other semiconductors, indium arsenide does not possess a barrier that obstructs the electrons of one material from gaining access to the other material. In this manner, aluminum’s superconductivity can make the top layers of indium arsenide, which is a semiconductor, to superconduct, as well.
“The device isn’t operating as a qubit yet, but this paper shows that it has the right ingredients to be a scalable technology,” stated Manfra, whose lab specializes in developing platforms for, and gaining insights into the physics behind, emerging quantum technologies.
Integrating the best properties of semiconductors and superconductors into planar structures, which could be readily adapted by the industry, could result in rendering quantum technology scalable. Currently trillions of switches, or transistors, on a single wafer enable classical computers to process information.
This work is an encouraging first step towards building scalable quantum technologies.
Michael Manfra, Bill and Dee O’Brien Chair Professor of Physics and Astronomy, Purdue University
Microsoft Corp. financially supported work at Purdue University.