Superconductor breakthrough at UCC could be significant for future of quantum computing

Scientists based in University College Cork (UCC), using one of the world’s most powerful quantum microscopes, have made a discovery that could have significant consequences for the future of computing – and the development of powerful quantum computers, in particular.

Quantum computers based on the rules of quantum physics – where matter exists as possibilities rather than certainties – can, unlike classical computers, perform innumerable, very fast calculations all at once, rather than in a linear fashion.

Researchers at UCC Macroscopic Quantum Matter Group laboratory have discovered a spatially modulating superconducting state in a new and unusual superconductor material uranium ditelluride (UTe2).

This new superconductor may provide a solution to one of quantum computing’s greatest challenges. Their findings have been published in the prestigious journal Nature.

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Lead author, Joe Carroll, a PhD researcher working with professor of quantum physics Séamus Davis, made the breakthrough.

“Superconductors are amazing materials which have many strange and unusual properties. Most famously, they allow electricity to flow with zero resistance. That is, if you pass a current through them, they don’t start to heat up. In fact, they don’t dissipate any energy, despite carrying a huge current,” he explained.

“They can do this because instead of individual electrons moving through the metal, we have pairs of electrons which bind together. These pairs of electrons together form macroscopic quantum mechanical fluid,” Mr Carroll added.

“What our team found was that some of the electron pairs form a new crystal structure embedded in this background fluid. These types of states were first discovered by our group in 2016 and are now called electron pair-density waves – a new form of superconducting matter, the properties of which we are still discovering.”

What was particularly exciting for them – and the wider community – was that UTe2 appears to be a new type of superconductor, he said.

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Physicists have been searching for a material like it for nearly 40 years. “The pairs of electrons appear to have intrinsic angular momentum. If this is true, then what we have detected is the first pair-density wave composed of these exotic pairs of electrons.”

Asked about the practical implications of this work, he noted: “There are indications that UTe2 is a special type of superconductor that could have huge consequences for quantum computing.”

Typical, classic computers use bits to store and manipulate information. “Quantum computers rely on quantum bits or qubits to do the same. The problem facing existing quantum computers is that each qubit must be in a superposition with two different energies – just as Schrödinger’s cat could be called both ‘dead’ and ‘alive’. This quantum state is very easily destroyed by collapsing into the lowest energy state – ‘dead’ – thereby, cutting off any useful computation,” he said.

“This places huge limits on the application of quantum computers. However, since its discovery five years ago, there has been a huge amount of research on UTe2 with evidence pointing to it being a superconductor which may be used as a basis for topological quantum computing.

“In such materials, there is no limit on the lifetime of the qubit during computation opening up many new ways for more stable and useful quantum computers. In fact, Microsoft have already invested billions of dollars into topological quantum computing so this is a well-established theoretical science already.”

“What the community has been searching for is a relevant topological superconductor. UTe2 appears to be that,” Mr Carroll said.

“What we’ve discovered then provides another piece to the puzzle of UTe2. To make applications using materials like this, we must understand their fundamental superconducting properties. All of modern science moves step by step. We are delighted to have contributed to the understanding of a material which could bring us closer to much more practical quantum computers.”

Prof John F Cryan, UCC vice-president for research and innovation, predicted the discovery would have significant consequences for the future of quantum computing.

“In coming weeks, the university will launch UCC Futures – Future Quantum and Photonics – and research led by Prof Davis and the Macroscopic Quantum Matter Group, with the use of one of the world’s most powerful microscopes, will play a crucial role in this exciting initiative,” he added.