Researchers at UChicago Pritzker School of Molecular Engineering, led by Professor Giulia Galli, and collaborators in Sweden have discovered that calcium oxide, a common compound, can be used to create nearly noiseless qubits, the building blocks of quantum computers. The team found that embedding atoms of bismuth within calcium oxide resulted in qubits with low levels of noise and long information retention times. This discovery, published in Nature Communications, could lead to more efficient and cost-effective quantum computing technologies. The team is now collaborating with experimental groups to test these findings.
Calcium Oxide: A Potential Medium for Quantum Computing
Calcium oxide, a common compound used in the production of cement, plaster, paper, and steel, may soon find its place in the realm of quantum computing. Researchers from the UChicago Pritzker School of Molecular Engineering, in collaboration with Swedish scientists, have discovered that single atoms of bismuth embedded in solid calcium oxide can function as qubits, the fundamental units of quantum computers and quantum communication devices. This discovery, published in Nature Communications, suggests that calcium oxide could be a cost-effective and efficient medium for storing quantum information.
The Search for the Ideal Qubit
A quantum bit, or qubit, is the basic unit of quantum information. It is typically composed of tiny point defects within semiconducting materials, some properties of which can be used to store information. However, many existing qubits are highly sensitive to their surroundings, with electronic or magnetic “noise” potentially altering their properties and erasing the encoded information.
In 2022, a collaboration between Japanese scientists and the groups of David Awschalom and Giulia Galli simulated the properties of over 12,000 materials to identify potential solids that could contain promising defects acting as qubits. Calcium oxide emerged as a potential candidate, with the ability to contain qubits that encoded information with very low levels of noise for an extended period of time.
Identifying the Perfect Defect
The next step for the researchers was to identify the ideal defect within the calcium oxide structure. Using a series of computational methods, the team screened over 9,000 different defects within calcium oxide for their potential as qubits. The results indicated that one type of defect, where an antimony, bismuth, or iodine atom is embedded within the usual structure of calcium and oxygen that make up calcium oxide, was particularly promising.
The Promise of Bismuth Defects
The team’s modeling approaches showed that the bismuth defect within calcium oxide could theoretically encode data with little noise and for relatively long periods of time. This is a significant improvement over many existing qubits, which only show milliseconds of coherence. Additionally, the material’s refractive index and its ability to emit photons of light suggest that it could integrate well with telecommunications devices.
Future Directions
While these findings are promising, they are still in the early stages. The researchers are now collaborating with experimental groups to construct the calcium-oxide-based materials and test whether the predictions hold true. Despite the preliminary nature of the research, the team believes that from a fundamental science perspective, this material holds great promise for the future of quantum computing.
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