Overcoming sensitivity to decoherence is a persistent stumbling block in efforts to build effective quantum computers. Now, a group of researchers from Chalmers University of Technology (Sweden) report progress in devising a superconductor able to host Majorana particles whose relative insensitivity to decoherence is a promising advantage.

The work is described in an account posted yesterday on Phys.org (Unconventional superconductor may be used to create quantum computers of the future). The basic idea is Majorana particles could become stable building blocks of quantum computers. The problem is they only occur under special circumstances. The Chalmers team, led by Floriana Lombardi, reported manufacturing a component that is able to host the sought-after particles.

“Majorana fermions are highly original particles, quite unlike those that make up the materials around us. In highly simplified terms, they can be seen as half electron. In a quantum computer the idea is to encode information in a pair of Majorana fermions which are separated in the material, which should, in principle, make the calculations immune to decoherence,” according to Phys.org.

In solid state materials, Majorana appear to occur only in topological superconductors. Microsoft is perhaps the best known of commercial organizations betting big on topological quantum computers. For a long time many doubted the existence of Majorana although evidence has been piling up in their favor (see HPCwire article, Neutrons Zero in on the Elusive Magnetic Majorana Fermion).

To create their unconventional superconductor, the Chalmers researchers started with a topological insulator made of bismuth telluride (Bi2Te3). The researchers placed a layer of aluminum, a conventional superconductor, on top, which conducts current entirely without resistance at low temperatures. The superconducting pair of electrons then leak into the topological insulator, which also becomes superconducting.

Initial measurements all indicated they had only induced standard superconductivity in the Bi2Te3 topological insulator, but when they cooled the component later to repeat some measurements the situation suddenly changed—the characteristics of the superconducting pairs of electrons varied in different directions.

“[That isn’t compatible at all with conventional superconductivity. Unexpected and exciting things occurred,” says Lombardi in the article. “For practical applications, the material is mainly of interest to those attempting to build a topological quantum computer. We want to explore the new physics hidden in topological superconductors – this is a new chapter in physics.”

Link to full account on Phys.org: https://phys.org/news/2018-02-unconventional-superconductor-quantum-future.html