A mathematical shortcut for determining when

A sleek new equation allows scientists to easily calculate the quantum information lifetimes of 12,000 different materials.

Scientists have discovered a mathematical shortcut to calculate a very important characteristic of quantum devices.

After calculating the quantum properties of 12,000 elements and compounds, the researchers published a new equation for estimating how long materials can retain quantum information, called “coherence time.”

“People have had to rely on complicated codes and calculations to predict the coherence times of spin qubits. But now people can self-calculate the prediction instantly. This opens up opportunities for researchers to find the next generation of qubit materials on their own. —Shun Kanai, Tohoku University

The elegant formula allows scientists to estimate the coherence times of materials in an instant – compared to the hours or weeks it would take to calculate an exact value.

The team, made up of scientists from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, the University of Chicago, Tohoku University in Japan, and Ajou University in Korea, published its results in April in the Proceedings of the National Academy of Sciences.

Their work is supported by the Center for Novel Pathways to Quantum Coherence in Materials, an Energy Frontier Research Center funded by the US Department of Energy, and by Q-NEXT, a DOE National Quantum Information Science Research Center led by Argonne.

The team’s equation applies to a particular class of materials – those that can be used in devices called spin qubits.

“People have had to rely on complicated codes and calculations to predict the coherence times of spin qubits. But now people can calculate the prediction by themselves instantly,” said study co-author Shun Kanai of Tohoku University. “This opens up opportunities for researchers to find the next generation of qubit materials on their own.”

Qubits are the fundamental unit of quantum information, the quantum version of classical computer bits. They come in different shapes and varieties, including a type called a spin qubit. A spin qubit stores data in a material’s spin – a quantum property inherent in all atomic and subatomic matter, such as electrons, atoms, and groups of atoms.

Scientists expect quantum technologies to help improve our daily lives. We might be able to send information over quantum communication networks that are impenetrable to hackers, or we might use quantum simulations to speed up drug delivery.

Realizing this potential will depend on the availability of sufficiently stable qubits – which have sufficiently long coherence times – to store, process and send the information.

Although the research team’s equation only gives a rough prediction of a material’s coherence time, it comes quite close to the actual value. And what the equation lacks in precision, it makes up for in convenience. It only requires five numbers – the values ​​of five particular properties of the material in question – to arrive at a solution. Plug them in and voila! You have your consistency time.

Diamond and silicon carbide are currently the most established materials for hosting spin qubits. Now scientists can explore other candidates without having to spend days calculating whether a material is worth investigating.

“The equation is like a lens. It tells you, “Look here, look at this material – it looks promising,” said Giulia Galli, a University of Chicago professor and Argonne senior scientist, study co-author and Q-NEXT collaborator. “We are looking for new qubit platforms, new materials. Identifying mathematical relationships like this indicates new materials to try, to combine.

With this equation in hand, the researchers plan to increase the accuracy of their model.

They will also be in contact with researchers capable of creating the materials with the most promising coherence times, testing whether they work as well as the equation predicts. (The team has already scored a success: a scientist outside the team reported that the relatively long coherence time of a material called calcium tungstate worked as predicted by the team’s formula.)

“Our findings help us advance current quantum information technology, but that’s not all,” said Hideo Ohno, a professor at Tohoku University, currently the university’s president and co-author of the item. “It will open up new possibilities by linking quantum technology to a variety of conventional systems, allowing us to make even more advances with the materials we already know. We are pushing more than one scientific frontier.

This work was a supported by the Center for Novel Pathways to Quantum Coherence in Materials, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, in conjunction with the U.S. Department of Energy Office of Science National Quantum Information Science Research Centers.

Q-NEXT is a U.S. Department of Energy National Quantum Information Science Research Center led by Argonne National Laboratory. Q-NEXT brings together world-class researchers from national laboratories, universities, and US technology companies with the sole purpose of developing science and technology to control and distribute quantum information. Q-NEXT collaborators and institutions will establish two national foundries for quantum materials and devices, develop networks of secure sensors and communication systems, establish simulation and network testbeds, and train a workforce. quantum-ready next-generation work to ensure continued American scientific and economic leadership. in this rapidly evolving field. For more information, visit https://​www​.​q​-next​.org.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts cutting-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state, and municipal agencies to help them solve their specific problems, advance American scientific leadership, and prepare the nation for a better future. With employees in more than 60 countries, Argonne is managed by UChicago Argonne, LLC for the US Department of Energy’s Office of Science.

U.S. Department of Energy Office of Science is the largest supporter of basic physical science research in the United States and strives to address some of the most pressing challenges of our time. For more information, visit https://​ener​gy​.gov/​s​c​ience.

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