How a physicist aims to reduce the noise in quantum computing

Ryan Behunin

Ever wondered why your credit score is what it is? Have you stored private information in the cloud that you want to remain that way? Thought about investing in cryptocurrency? Worried about cyber warfare?

If you answered yes to any of these questions, quantum computing plays a role in your life—or at least, it will when its usage becomes practical enough to run the systems that run our daily lives.

That’s where Ryan Behunin’s work comes in.

Behunin, an assistant professor of applied physics and materials science and a researcher in NAU’s Center for Materials Interfaces in Research & Applications (¡MIRA!), explores fundamental questions about the interaction of light, sound and matter. His latest research project, “Controlling noise in quantum devices with light and sound,” was funded with an almost $500,000 NSF CAREER grant, which supports early-career faculty in their groundbreaking research.

This work targets challenges to realizing practical quantum computers by helping the building blocks of quantum computers, termed “qubits,” perform better. That is critical because quantum computers have the potential to solve certain problems that are not tractable using traditional computing technology. The challenge is that, currently, the technology is too vulnerable to disturbances in the environment that corrupt the information stored in quantum computers—too full of noise, as it were—to reach its full potential.

Behunin’s goal is to quiet that noise.

“Theoretically, quantum physics can enable powerful new computers that achieve massive exponential speedups over traditional forms of computing, permitting calculations that currently are intractable” Behunin said. “Practically, however, the very quantum features that enable these remarkable properties are rapidly erased by process termed decoherence, which is not unlike the way a plucked guitar string eventually relaxes.”

As a result, decoherence limits the lifetime of quantum states, posing challenges for practical quantum technologies. This project will show how decoherence can be controlled by manipulating sound waves.

“Noise” in quantum mechanics operates much like static on the radio, making it difficult to “hear” the signal. The most problematic source of noise for many quantum devices is from two-level tunneling states, or TLSs. They’re not well understood, but they are everywhere, and physicists have yet to find an effective way to quiet TLSs. This research will leverage the strong interaction between TLSs and sound waves to develop new techniques that control and reduce this source of noise.

The answers Behunin is looking for have implications for cybersecurity, advanced manufacturing and areas like drug development; faster, more accessible quantum computing could mean faster and more affordable creation of drugs or other organic materials.

“We can take a big step toward practical quantum technology if we can show how noise can be controlled and reduced in quantum devices,” Behunin said.

This project also will focus on giving research opportunities to students from populations that are historically underrepresented in the field of physics, including women and minority groups. In addition to its groundbreaking research, ¡MIRA!’s mission is to increase diversity in these fields. Recruiting students into labs like Behunin’s is a big part of that mission, as is outreach to K-12 students to get them excited about STEM research long before they enter college. That’s why part of this project includes Behunin teaching a free mini course on quantum physics at Tynkertopia, a nonprofit STEAM center located in Flagstaff’s Sunnyside neighborhood.

“Scientifically, we’re trying to answer deep materials science questions—namely, what are TLSs and how can we get rid of them?” Behunin said. “With regard to diversity, this project aims to engage communities that are underrepresented in the sciences. The goal is to increase access and exposure to quantum science in our underserved communities.”

Learn more about ¡MIRA!.

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Heidi Toth | NAU Communications
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NAU Communications