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Researchers led by UChicago Pritzker School of Molecular Engineering Professor Giulia Gall, together with collaborators in Sweden, used theoretical and computational approaches to discover how defects in simple calcium oxide can produce qubits with a handful of promising properties. Credit: UChicago Pritzker School of Molecular Engineering / Peter Allen, edited
Researchers discovered that bismuth atoms embedded in calcium oxide can function as qubits for quantum computers, providing a low-noise, durable, and inexpensive alternative to current materials. This groundbreaking study highlights its potential to transform
Calcium oxide, also known as quicklime, is a white, caustic, alkaline chemical compound derived from limestone and other calcium-rich materials. It is primarily used in the production of cement and mortar, as well as in the steel industry, for water treatment, and in the manufacture of glass, ceramics, and paper. When mixed with water, it reacts exothermically to form calcium hydroxide, commonly known as slaked lime.
Advancements in Qubit Development
A quantum bit, or qubit, is the basic unit of information that encodes data in quantum computing. Today, researchers have developed many different types of qubits, which are often composed of tiny point defects within semiconducting materials. Some of the properties of these defects can be used to store pieces of information. However, many existing qubits are incredibly fragile; electronic or magnetic “noise” in their surroundings can change their properties, erasing any information that was encoded within them.
In 2022, a collaboration between scientists in Japan and the groups of David Awschalom and Galli simulated the properties of more than 12,000 materials to discover new potential solids that could contain promising defects acting as qubits. That work turned up calcium oxide as one of a number of materials with the potential to contain qubits that encoded information with very low levels of noise for an especially long period of time.
Discovering New Quantum Materials
“Our previous work told us that if you find the right defects to put within its structure, calcium oxide would be a perfect medium for storing quantum information,” said Nikita Onizhuk, a postdoctoral fellow in the Galli group and one of the authors of the paper. “So our new goal was to find the ideal defect.”
In the new paper, Galli and her colleagues used a series of computational methods that were established over recent years to screen more than 9,000 different defects within calcium oxide for their potential as qubits. The results pointed toward one type of defect — in which an antimony, bismuth or iodine DOI: 10.1038/s41467-024-49057-8
Funding: This work was supported by the Swedish e-science Research Centre (SeRC), the Knut and Alice Wallenberg Foundation, the Swedish Research Council, a Google PhD Fellowship, and the Air Force Office of Scientific Research.