Scientific discovery at Quantum Foundry

Researchers at the National Science Foundation's first Quantum Foundry at the University of California Santa Barbara are making major breakthroughs in the development of materials that enable quantum information-based technologies for quantum computing, communications, sensing, and simulation.

The difficulty with quantum mechanics – deemed the hardest part of physics – is that quantum behavior does not follow the rules we are used to when it comes to conventional physics.

Things like quantum entanglement where regardless of distance, entangled particles stay connected in a sense or even the observed anti-gravity effects with quantum locking are some of the strange phenomena scientists have witnessed during the study of this seemingly impossible branch of physics.

A new paper published in "Nature Materials," has detailed a new material developed in the Quantum Foundry as a candidate superconductor – a material in which electrical resistance disappears and magnetic fields are expelled – that could leverage the strange properties found in the quantum realm for future computers and other devices in the easier to observe and understand universe.

A previous paper published by the same group under Professor Stephen Wilson at Princeton University, described a new material, cesium vanadium antimonide, that exhibits a surprising mixture of characteristics involving a self-organized patterning of charge intertwined with a superconducting state.

The most recent paper details those shared characteristics in another new material, a mixture of potassium, vanadium, and antimony, which could jumpstart quantum computing.

Materials in this group of compounds, Wilson noted, "are predicted to host interesting charge density wave physics [that is, their electrons self-organize into a non-uniform pattern across the metal sites in the compound]. The peculiar nature of this self-organizing patterning of electrons is the focus of the current work."

Fundamentally, this material could be used to create atomic magnetic fields that operate within small, controlled loops.

While there is significantly more physics behind this process, the research team was able to use high-resolution scanning tunneling microscopy to identify what they believe to be the signatures of such a state.

This is exactly the kind of work for which the Quantum Foundry was established.

"The foundry's contribution is important," said Wilson. "It has played a leading role in developing these materials, and foundry researchers discovered superconductivity in them and then found signatures indicating that they may possess a charge density wave. Now, the materials are being studied worldwide, because they have various aspects that are of interest to many different communities."

The excitement has spread throughout the academic community, as this new phenomenon provides clues to many different fields.

"They are of interest, for instance, to people in quantum information as potential topological superconductors (topology is often used in mathematics for theoretical physics, where different spaces exist and the matter in those spaces differ between each space)," Wilson continued. "They are of interest to people who study new physics in topological metals, because they potentially host interesting correlation effects, defined as the electrons' interacting with one another, and that is potentially what provides the genesis of this charge density wave state."

This charge density wave state is the self-organization of electrons into non-uniform patterns across the metallic sites in a compound. The conductivity of the metal attracts the electrons, yet they behave in ways still not fully understood.

"And they're of interest to people who are pursuing high-temperature superconductivity, because they have elements that seem to link them to some of the features seen in those materials even though KV3SB5 [potassium, vanadium and antimony], superconducts at a fairly low temperature," finished Wilson.

If this new compound is capable of doing what it is suspected of, it could be used to make a topological qubit useful in quantum information applications, meaning this material could be used to create functional atomic binary in a static space that functions independently and part of whatever it is being used for, in this case, superconductors.

"There are only certain kinds of states you can find that can serve as a topological qubit, and a topological superconductor is expected to host one," Wilson added. "Such materials are rare. This system may be of interest for that, but it's far from confirmed, and it's hard to confirm whether it is or not. There is a lot left to be done in understanding this new class of superconductors."