Quantum control with light paves way for ultra-fast computers

Terahertz light can control some of the essential quantum properties of superconducting states, report researchers.

Jigang Wang patiently explains his latest discovery in quantum control that could lead to superfast computing based on quantum mechanics: He mentions light-induced superconductivity without energy gap. He brings up forbidden supercurrent quantum beats. And he mentions terahertz-speed symmetry breaking.

Then he backs up and clarified all that. After all, the quantum world of matter and energy at terahertz and nanometer scales—trillions of cycles per second and billionths of meters—is still a mystery to most of us.

“I like to study quantum control of superconductivity exceeding the gigahertz, or billions of cycles per second, bottleneck in current state-of-the-art quantum computation applications,” says Wang, a professor of physics and astronomy at Iowa State University. “We’re using terahertz light as a control knob to accelerate supercurrents.”

A bit more explanation

Superconductivity is the movement of electricity through certain materials without resistance. It typically occurs at very, very cold temperatures. Think -400 Fahrenheit for “high-temperature” superconductors.

Terahertz light is light at very, very high frequencies. Think trillions of cycles per second. It’s essentially extremely strong and powerful microwave bursts firing at very short time frames.

It all sounds esoteric and strange. But the new method could have very practical applications.

“Light-induced supercurrents chart a path forward for electromagnetic design of emergent materials properties and collective coherent oscillations for quantum engineering applications,” Wang and his coauthors write in a paper in Nature Photonics.

In other words, the discovery could help physicists “create crazy-fast quantum computers by nudging supercurrents,” Wang writes in a summary of the research team’s findings.

Controlling quantum physics

Finding ways to control, access, and manipulate the special characteristics of the quantum world and connect them to real-world problems is a major scientific push these days. The National Science Foundation has included the “Quantum Leap” in its “10 big ideas” for future research and development.

“By exploiting interactions of these quantum systems, next-generation technologies for sensing, computing, modeling, and communicating will be more accurate and efficient,” says a summary of the science foundation’s support of quantum studies. “To reach these capabilities, researchers need understanding of quantum mechanics to observe, manipulate, and control the behavior of particles and energy at dimensions at least a million times smaller than the width of a human hair.”

The researchers are advancing the quantum frontier by finding new macroscopic supercurrent flowing states and developing quantum controls for switching and modulating them.

A summary of the research team’s study says experimental data they obtained from a terahertz spectroscopy instrument indicates terahertz light-wave tuning of supercurrents is a universal tool “and is key for pushing quantum functionalities to reach their ultimate limits in many cross-cutting disciplines” such as those mentioned by the science foundation.

And so, the researchers write, “We believe that it is fair to say that the present study opens a new arena of light-wave superconducting electronics via terahertz quantum control for many years to come.”

The Army Research Office supports Wang’s research. Additional researchers from Iowa State, the University of Wisconsin-Madison, and the University of Alabama at Birmingham contributed to the work.

Source: Iowa State University

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