Unusual superconductor will change the way a quantum computer is built

Researchers at the University of Maryland Center for Quantum Materials and their colleagues have shown that uranium ditelluride, or UTe2 for short, can be used as a superconductor to create quantum computers and other futuristic devices.

All superconductors carry electric currents without resistance. But they achieve their superconductivity in different ways. Since the early 2000s, scientists have been looking for a special kind of superconductor that relies on the complex mechanics of current-carrying subatomic particles.

Superconductivity is a macroscopic quantum phenomenon, which consists in the phase transition of some substances at low temperatures to a new state with zero electrical resistance. There are several different types of superconductors. The simplest of these are some pure metals, whose properties change near absolute zero, and their behavior is well described by the Bardeen-Cooper-Schrieffer (BCS) theory.

A study by a team from Stanford University shows that in UTe2 or uranium ditelluride, not one, but two types of superconductivity exist simultaneously.

In another study, a team led by Steven Anlage, UMD professor of physics and QMC member, found unusual behavior on the surface of the same material.

Superconductors only show their special characteristics at a certain temperature, just as water freezes only below zero Celsius. In conventional superconductors, electrons are combined into a two-person kong line, following each other inside the metal. But in some rare cases, pairs of electrons are not built in a row, but dance around each other. As soon as electrons combine in this way, a vortex is formed, it is he who distinguishes a topological superconductor from a simple electronic one.

In a new research paper, Palone and his collaborators reported two new dimensions that reveal the internal structure of UTe2. The UMD team measured the specific heat of a material, which measures how much energy it takes to heat it per degree. They measured the specific heat at different initial temperatures and observed how it changes as the sample becomes superconducting.

During the second measurement, the Stanford team aimed a laser beam at the UTe2 chunk and noticed that the reflected light was slightly distorted. If they sent light bouncing up and down, the reflected light bounced mostly up and down, but also slightly left and right. This meant that something inside the superconductor was twisting the light and not spinning it out.

The Stanford team also discovered that a magnetic field can cause UTe2 to bend light in one way or another. If they applied an upward magnetic field when the sample became superconducting, the outgoing light would be tilted to the left. If they directed the magnetic field downward, the light tilted to the right. This told the researchers that there was something special about the up and down directions of the crystal for the electrons in pairs inside the sample.

If the nature of superconductivity in a material is topological, the resistance in the bulk of the material will still be zero, but something unique will happen on the surface: particles known as Majorana modes will appear, they will form a liquid that is not a superconductor. These particles also remain on the surface despite material defects or minor environmental disturbances.

The researchers suggested that due to the unique properties of these particles, they could be a good basis for quantum computers. Encoding a piece of quantum information into several majoranas located far from each other makes the information virtually immune to local perturbations, which until now have been one of the main problems of quantum computers.

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Alexandr Ivanov earned his Licentiate Engineer in Systems and Computer Engineering from the Free International University of Moldova. Since 2013, Alexandr has been working as a freelance web programmer.
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Alexandr Ivanov

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