New quantum visualization technique to identify materials for next generation quantum computing

The significant breakthrough means that, for the first time, researchers have found a way to determine once and for all whether a material can effectively be used in certain quantum computing microchips.

The major findings have been published today in the academic journal Science and are the result of a large international collaboration which includes leading theoretical work from Prof. Dung-Hai Lee in University of California, Berkeley, and material synthesis from professors Sheng Ran and Johnpierre Paglione in Washington University in St. Louis and the University of Maryland respectively.

Using equipment found in only three labs around the world, researchers at the Davis Group based in UCC were able to definitively determine whether Uranium ditelluride (UTe ₂), which is a known superconductor, had the characteristics required to be an intrinsic topological superconductor.

A topological superconductor is a unique material that, at its surface, hosts new quantum particles named Majorana fermions. In theory they can be used to stably store quantum information without being disturbed by the noise and disorder which plague present quantum computers. Physicists have been on the hunt for an intrinsic topological superconductor for decades, but no material ever discovered has ticked all the boxes.

UTe ₂ had been considered a strong candidate material for intrinsic topological superconductivity since its discovery in 2019 however no research had definitively evaluated its suitability -- until now.

Using a scanning tunneling microscope (STM) operating in a new mode invented by Séamus Davis, Professor of Quantum Physics at UCC, a team led by Joe Carroll, a PhD researcher at the Davis Group and Kuanysh Zhussupbekov, a Marie Curie postdoctoral fellow, were able to conclude once and for all whether UTe ₂ is the right sort of topological superconductor.

The experiments carried out using the "Andreev" STM -- found only in Prof. Davis' labs in Cork, Oxford University in the UK, and Cornell University in New York -- discovered that UTe ₂ is indeed an intrinsic topological superconductor, but not exactly the kind for which physicists have been searching.

However, the first-of-its-kind experiment is a breakthrough in itself.

When asked about the experiment Mr. Carroll described it as follows "Traditionally researchers have searched for topological superconductors by taking measurements using metallic probes. They do this because metals are simple materials, so they play essentially no role in the experiment. What's new about our technique is that we use another superconductor to probe the surface of UTe₂. By doing so we exclude the normal surface electrons from our measurement leaving behind only the Majorana fermions."

Carroll further highlighted that this technique would allow scientists to determine directly whether other materials are suitable for topological quantum computing.

Quantum computers have the capacity to answer in seconds the kind of complex mathematical problems that would take current generation computers years to solve. Right now, governments and companies around the world are racing to develop quantum processors with more and more quantum bits but the fickle nature of these quantum calculations is holding back significant progress.

Earlier this year Microsoft announced the Majorana 1, which the company has said is "the world's first Quantum Processing Unit (QPU) powered by a Topological Core ."

Microsoft explained that to achieve this advance, synthetic topological superconductors based on elaborately engineered stacks of conventional materials were required.

However the Davis Group's new work means that scientists can now find single materials to replace these complicated circuits, potentially leading to greater efficiencies in quantum processors and allowing many more qubits on a single chip thus moving us closer to the next generation of quantum computing.