Researchers explore subtleties in superconductors in hopes of supporting development of quantum computers

Ryan Day is studying superconductors. Materials that conduct perfect electricity do not lose energy from heat and resistance. In particular, a scientist at the University of California, Berkeley, is studying how superconductors can coexist with their opposites; insulating materials that stop the flow of electrons.

The materials that combine these two opposing states, called topological superconductors, are understandably strange, difficult to characterize and design, but if one can design them correctly, they could play an important role in quantum computing.

“Every computer is prone to errors, and it’s no different when you switch to quantum computing – it just gets a lot harder to manage. Topological quantum computing is one of the platforms thought to be able to circumvent many of the most common sources of error, “says Day,” but topological quantum computing requires us to produce a particle that has never been seen before in nature. . “

The day came at a Canadian light source at the University of Saskatchewan to use the QMSC beam line, a facility built to study exactly these types of issues in quantum materials. The possibilities were developed under the guidance of Andrea Damacelli, research director at the Stuart Blueson Institute for Quantum Matter at UBC, with whom Day was a doctoral student during this study.

“QMSC is designed to have very fine control over a very wide range of energies, so you can really get extremely accurate information about electrons as they move in all possible directions,” Day said.

His experiment, conducted at temperatures about 20 degrees above absolute zero, aimed to resolve conflicting results in existing research on superconductors with topological states.

“The experiments that were done before ours were really good, but there were some contradictions in the literature that needed to be better understood,” he explained. The relative novelty of the field, combined with the unusual properties that the materials show in the energy ranges used for this study, meant that it was difficult to discern what was happening to the topological states.

In his experiments, Day observed that topological states are embedded in a large number of other electronic states that inhibit lithium iron arsenide, the superconducting material he studies, from exhibiting topological superconductivity. Based on his measurements in CLS, he suggested that this problem be circumvented by simply stretching the material.

The results of this work published in Physical examination B, provide additional evidence that lithium iron arsenide maintains topological states on its surface, which is key to the potential use of the material in quantum calculations. It also reveals potential challenges to engineering materials for these applications, an area for future research.

“By doing these experiments, we can understand this material in a much better way and start thinking about how we can actually use it, and then hope that someone builds a quantum computer with it and everyone wins.