Pivotal Discovery Could Open New Field of Quantum Technology Called “Magnonics”

University of Chicago, Argonne Scientists Tame Photon-Magnon Interactions

In a first-of-its-kind discovery, researchers in the University of Chicago’s Pritzker School of Molecular Engineering and Argonne National Laboratory announced they can directly control the interactions between two types of quantum particles called microwave photons and magnons. The approach may become a new way to build quantum technology, including electronic devices with new capabilities. 

Scientists have high hopes for quantum technology, which has advanced by leaps and bounds over the past decade and could become the basis of powerful new types of computers, ultra-sensitive detectors, and even “hack-proof” communication. But challenges remain in scaling up the technology, which depends on manipulating the smallest particles in order to harness the strange properties of quantum physics.

Two such quantum particles are microwave photons—elementary particles that form the electromagnetic waves that we already use for wireless communications—and magnons. Magnons are the term for a particle-like entity that forms what scientists call ​“spin waves” — wave-like disturbances that can occur in magnetic materials, and can be used to move information.

Getting these two types of particles to talk to each other has emerged in recent years as a promising platform for both classical and quantum information processing. But this interaction had proved impossible to manipulate in real time, until now.

“Before our discovery, controlling the photon-magnon interaction was like shooting an arrow into the air,” said Xufeng Zhang, a scientist in the Center for Nanoscale Materials at Argonne National Laboratory and the corresponding author of the study. ​“One has no control at all over that arrow once in flight.”

The team’s discovery has changed that. ​“Now, it is more like flying a drone, where we can guide and control its flight electronically,” said Zhang.

Tunable Interaction: The Big Leap

Through smart engineering, the team employs an electrical signal to periodically alter the magnon vibrational frequency and thereby induce effective magnon-photon interaction. The result is the first-ever microwave-magnonic device that scientists can “tune” to their wishes.

The team’s device can control the strength of the photon-magnon interaction at any point as information is being transferred between photons and magnons. It can even completely turn the interaction on and off. With this tuning capability, scientists can process and manipulate information in ways that far surpass current versions of hybrid magnonic devices.

“Before our discovery, controlling the photon-magnon interaction was like shooting an arrow into the air.”

 Xufeng Zhang, Argonne Center for Nanoscale Materials

“Researchers have been searching for a way to control this interaction for the past few years,” said Zhang.

Real-Time Quantum Signal Processing

The team’s discovery opens a new direction for magnon-based signal processing and should lead to electronic devices with new capabilities.

It may also enable important applications for quantum signal processing, where microwave-magnonic interactions are being explored as a promising candidate for transferring information between different quantum systems.

The study’s other authors are Changchun Zhong and Liang Jiang of the University of Chicago, and Jing Xu, Xu Han and Dafei Jin with Argonne National Laboratory.

Reference: “Floquet Cavity Electromagnonics” by Jing Xu, Changchun Zhong, Xu Han, Dafei Jin, Liang Jiang and Xufeng Zhang, 1 December 2020, Physical Review Letters.
DOI: 10.1103/PhysRevLett.125.237201

Funding: U.S. Department of Energy Office of Basic Energy Sciences, U. S. Army Research Laboratory, Army Research Office, Air Force Office of Scientific Research, National Science Foundation, Packard Foundation.

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