Split personality of superconductor material offers possibilities for quantum computing

A superconductor has been observed which has two electronic identities at once offering a revolutionary way for next-generation electronics to store and process information, with particular relevance to quantum computers.

The new material is a crystal that has been described as being part superconductor and part metal, named a “topological superconductor” by scientists at Princeton University.  When at very low temperatures the crystal’s interior conducts electricity with no resistance as a normal superconductor would.  However the surface is metallic, and therefore has resistance to any current carried.

Usually materials are either in one category or another, be it metal, insulator or superconductor and so will consistently provide the same amount of resistance, according to M. Zahid Hasan, an associate professor of physics at Princeton.

“The known states of electronic matter are insulators, metals, magnets, semiconductors and superconductors, and each of them has brought us new technology. Topological superconductors are superconducting everywhere but on the surface, where they are metallic; this leads to many possibilities for applications.”

Princeton says that one of the most exciting potential uses for the material would be in energy-efficient quantum computers that would have the ability to identify errors in calculation as they occur and resist them during processing.

Fundamental to being able to do this is manipulating Majorana fermions, the catch being that they have been predicted over 70 years ago, though not actually observed.  It is thought that the dual electronic personality of a superconductor with different surface properties may allow electrons on the surface to become Majorana fermions, according to Hasan. 

According to physicist Charles Kane of the University of Pennsylvania, if a topological superconductor were to be placed in contact with a topological insulator, some of the electrons at the interface could become long-sought Majorana fermions if the composite material were placed into a very strong magnetic field.

This is a process that could take many years to refine however, with Hasan adding that “it takes time to go from new physics to new technology — usually 20 to 30 years, as was the case with semiconductors.”

According to L. Andrew Way the split personality of such an unusual superconductor lends itself well to quantum computing.

“These highly unusual superconductors are the most ideal nurseries to create and manipulate Majorana fermions, which could be used to do quantum computing in a fault-resistant way.  And because the particles would exist on a superconductor, it could be possible to manipulate them in low power-consumption devices that are not only ‘green,’ but also immune to the overheating problems that befall current silicon-based electronics,” said Way.