Unconventional Superconductors Can Become Material For Future Quantum Computers

With its insensitivity to interference, so-called majoranaparticles could become stable building blocks in a quantum computer. The problem is that they only occur under very special circumstances. Now, chalmers researchers have managed to produce a component that shows clear signs of housing the sought-after particles.

Scientists all over the world are struggling to build a quantum computer. One of the major challenges is to get around the quantum systems sensitivity to interference. A trace in quantum computer research is therefore to utilize so-called majoranaparticles, also known as majoranera mermaids. Among other things, Microsoft is committed to developing this kind of quantum computer.

Majoranafermions are very original particles, quite different ones that build up the materials around us. Very simplified, they can be compared to half of electrons. In a quantum computer, the idea is to encode information in pairs of major ananermic ions that are separated in the material, which would make the calculations in principle immune to interference.

So where do you find majoranaferions?

In solid materials, they teach only in so-called topological superconductors - a type of superconductor that is so new and special that it is barely in practice. But a research group at Chalmers is now among the first in the world to present results that indicate that they have actually managed to manufacture a topological superconductor.

"Our experimental results are completely compatible with topological superconductivity," said Floriana Lombardi, Assistant Professor at the Department of Quantum Component Physics at Chalmers.

In order to create their unconventional superconductors, they originated from a so-called topological isolator of bismuthelluride, Be2Te3. A topological isolator is mostly an insulator - that is, it does not conduct current - but conducts current in a very special way on the surface. On top of this, the researchers have added a layer of a conventional superconductor, in this case aluminum, which conducts power without resistance at really low temperatures.

"The superconducting pairs of electrons then leak into the topological isolator that also becomes superconducting," explains Thilo Bauch, associate professor of quantum component physics.

At the first measurements, everything indicated that they only had normal superconductivity in their component. Although they later cooled down the component again, to routinely repeat some measurements, the situation was suddenly different - the properties of the superconducting electron pairs varied in different directions.

"And it does not go hand in hand with conventional superconductors. Suddenly unexpected and exciting things had appeared, "said Floriana Lombardi.

Unlike other research groups, Floriana Lombardi's group had used platinum to assemble the topological insulator with the aluminum. In case of repeated cooling it caused tension in the material (see figure), which caused the superconductor to change its character.

After an intensive analysis period, the research team found that they probably managed to create a topological superconductor.

- For practical applications, the material is primarily interesting for those who try to build a topological quantum computer. We want to explore all the new exciting physics that hide in topological superconductors - this is a new chapter in physics, says Floriana Lombardi.

The results were published recently in the scientific journal Nature Communications: Induced unconventional superconductivity on the surface states of Bi2Te3 topological isolator

More about quantum computers and majoranaparticle
At Chalmers, a large quantum computer project is under way at Wallenberg Quantum Technology Center . However, it is based on technology other than topological superconductors.

Majoranaparticle was predicted by the Italian physicist Ettore Majorana in 1937. It is a very original elementary particle - like electrons, neutrons and protons - belong to the group of fermions. Unlike all other fermions, the majoran anthem is its own antipartikel.