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Researchers have determined how to use magnons—collective vibrations of the magnetic spins of atoms—for next-generation information technologies, including quantum technologies with magnetic systems.

From the computer hard drives that store our data to the motors and engines that drive power plants, magnetism is central to many transformative technologies. Magnetic materials are expected to play an even larger role in new technologies on the horizon: the transmission and processing of quantum information and the development of quantum computers.

New research led by scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory developed an approach to control the collective magnetic properties of atoms in real time and potentially deploy them for next-generation information technologies. This discovery could aid in developing future quantum computers, which can perform tasks that would be impossible using today's computers, as well as "on chip" technologies—with magnetic systems embedded on semiconductor chips, or "on chip."

The Argonne-led team's breakthrough exploits the fact that every atom has its own magnetic spin—like a miniature compass needle. When these spins all move together, they create a wave or "excitation" called a magnon. The researchers' method makes it possible to control magnons in real time, harnessing their information-processing potential.

"These capabilities are essential for advancing quantum communication and computing," said Yi Li, an Argonne assistant scientist and a lead author of the study reporting these results.

Two papers based on the research were published in April in and .

For this research, the scientists used two small magnetic spheres made of a material called yttrium iron garnet. They connected the spheres on a chip with a superconducting resonator. This setup allowed the researchers to send and receive magnon signals between the two distant spheres.

The team sent out a single pulse of energy, which traveled back and forth between the two spheres in sync with each other. This oscillation showed that energy can be transferred "coherently" or in a well-understood pattern between the spheres, much like a clear telephone conversation between two people speaking from afar.

The researchers discovered that if two energy pulses were sent through the magnetic chip setup, the pulses either mutually strengthened each other or one pulse canceled the other, depending on the time delay between them. These findings showed that magnons can interfere with each other, similar to how waves in water can create patterns when they overlap.

Additionally, the team found that this interference property persists because the two spheres are able to remain magnetically "coupled," or capable of storing the energy from the pulses traveling between them. This is similar to how a quantum state can transfer between two qubits—or quantum bits—in a quantum computer.

Furthermore, by sending multiple energy pulses, the scientists created intricate interference patterns, similar to the appearance of light when diffracted into different beams. This shows the potential for complex signal and transmission operations using magnons.

The team's findings indicated that magnetic excitation in their on-chip setup achieved what Li called "nearly perfect interference"—a key requirement for harnessing the potential of magnons in a variety of settings. Their approach could open new ways of processing information using magnons, with implications for the development of quantum computers and other advanced technologies.

"This work shows how magnetic excitations can be transferred remotely and perform interference operations in real time, potentially benefiting quantum computing," Li said. "While the true potential isn't clear yet, it provides a prototype model for future exploration."

The use of magnetic materials to process quantum information could empower a quantum computer with supplemental functionalities that are specific to those systems. For example, magnetic materials could be used to build on-chip isolators that help suppress quantum "noise" and improve clarity in a quantum computer. They could also convert microwave signals into optical signals, which is crucial for connecting different parts of a quantum system.

"There are challenges and opportunities in materials science and understanding physics. This work is about beautiful physics on a chip, involving superconducting circuits and low-damping magnetic materials. It's a significant piece of work," said Argonne Distinguished Fellow Valentine Novosad, a senior materials scientist and another author of the study.

This new research builds on previous papers published in 2019 and 2022 to further explore how to couple magnetization and superconductivity, and how magnons in yttrium iron garnet spheres can be manipulated to store information and for sophisticated information-processing tasks.

The magnonic devices were fabricated at the Center for Nanoscale Materials, a DOE Office of Science user facility at Argonne.