10/12/2026 Argonne National Laboratory
Founder Professor Axel Hoffmann and colleagues at Argonne National Laboratory have demonstrated, for the first time, that spin waves in a thin film of epitaxial yttrium iron garnet (YIG) can be coupled to a superconducting resonator fabricated directly on top of it, creating a hybrid system that supports one-way propagation of signals. Overcoming a key materials challenge by switching to a substrate free of microwave-absorbing rare-earth metals, the team showed that this platform works, an important step toward integrating magnetic spins into compact, on-chip quantum information technologies.
Written by Argonne National Laboratory
Quantum information systems could one day shape everyday life through faster computing, sharper sensing and more secure communication. A new result from the U.S. Department of Energy’s Argonne National Laboratory and the University of Illinois Urbana-Champaign marks an important step for magnetic spins — a quantum property of matter that can be used to store and manipulate information — to play a role in the future of quantum information processing.
The researchers show that the ripples in the magnetic state of a material, called spin waves, can interact with superconducting circuits, a tiny electrical circuit that can carry microwave signals. The result is a hybrid system in which these two different ways of carrying information can interact and work together.
One can think of it like a hybrid car: A combustion gas engine and an electric motor operate in fundamentally different ways, but a hybrid vehicle connects them so they can work together. Similarly, the new quantum system brings together magnetic spin waves and superconducting circuits, potentially allowing researchers to combine the strengths of both.
“This is the first time we’ve shown the proof of concept, demonstrating that we can couple spin waves to a superconducting resonator,” said Yi Li, an Argonne scientist and first author of the paper, published in Physical Review Letters.
Superconducting circuits, standard parts of many quantum information systems, help connect and control signals inside those systems. One way to picture them is as tiny on-chip antennas: They send and receive microwave signals in a way that strengthens communication with other parts of the device. That role makes them especially important in quantum computing, where information carried in quantum states can be fragile.
Spin waves offer a different advantage. Under certain conditions, spin waves are unidirectional, meaning they naturally prefer one direction of travel over the opposite direction. That is useful because quantum systems often need one-way signal control to help prevent unwanted noise from leaking back into the quantum components.
“One-way propagation is important because it can help guide information in a single direction and reduce unwanted return signals,” Li said. “That kind of control is valuable for quantum information science, and now we can integrate this function onto a superconducting circuit.”
At the heart of the experiment is a device built on a thin magnetic film, which provides a path for spin waves to travel. The film is made of epitaxial yttrium iron garnet, or YIG, nature’s most efficient material for sustaining magnetic motion: It loses very little energy as those motions travel through it. A second layer — the superconducting circuit — is fabricated directly on top of the magnetic film. As the spin wave travels through the film, it excites microwaves in the circuit above it. The circuit — our efficient on-chip antenna — is tuned to interact with the spin wave in the thin magnetic film. Thus the spin waves and superconducting circuit are wed.
“Everything that is happening around us, everything we know, everything that comes to us comes in the form of a wave,” said Argonne Distinguished Fellow Valentine Novosad, an Argonne scientist and the paper’s lead corresponding author. “This work is one example where we use magnetic excitations, which are spin waves in magnetic materials patterned in a chip, and make them communicate with a different kind of electromagnetic wave that lives in a superconducting resonator.”
This design enables strong coupling between spin waves and microwaves. It also enables one-way propagation of a hybrid mode, a strategy that enables information carried in a superconducting circuit to travel along one direction rather than the other.
“In quantum information engineering, we dig into in different material systems to explore exotic material properties, see which materials can do something special or power modern technologies,” said Founder Professor Axel Hoffmann of the Department of Materials Science and Engineering at The Grainger College of Engineering, and paper corresponding author. “So for our work, the question is, what can we do with magnetic material to do something special?”
In previous related research, magnetic spins have been coupled to superconducting circuits in a collective motion called a Kittel mode. This mode is relatively straightforward to couple to a superconducting circuit, but it does not naturally allow signals to travel in only one direction.
In this latest paper, the team was able to make the spin waves travel through the thin film and continue their journey as microwaves in the superconducting circuit. That makes the approach more relevant for compact, on-chip systems that could form part of future quantum technologies.
The materials challenge was significant. Many magnetic materials lose energy too quickly for this kind of application, and the problem can lie with the substrate — the physical platform beneath the magnetic film. Common substrates for high-quality YIG film growth contain rare-earth metals that absorb microwave signals at low temperatures, draining energy from the system. The team found that switching to a substrate without rare-earth metals allowed the device to work as intended.
“Nobody had succeeded in doing so before because of the materials challenge. Now we’ve shown that this platform works,” Li said.
The result links two active research areas: spin-wave magnonics and superconducting quantum circuits. The former explores fundamental physics in materials science; the latter focuses on microwave engineering for information processing. Researchers see it as a promising way of expanding basic science for quantum information science.
“This is a new field, an emerging field, and it is attracting attention around the world,” Novosad said. “We see this result as part of a bright future for hybrid systems connected to quantum information science.”
Fabrication of the superconducting resonators was performed at the Center for Nanoscale Materials, a DOE Office of Science user facility at Argonne.
Co-authors with Li, Novosad and Hoffmann are Tomas Polakovic, Ralu Divan, Ulrich Welp and Charudatta Phatak at Argonne; Jinho Lim, Xingzhi Wang and Jian-Min Zuo at the University of Illinois Urbana-Champaign; Carissa Kiehl at Carthage College; Kab-Jin Kim and Moojune Song at the Korea Advanced Institute of Science and Technology; and Phuoc Cao Van and Jong-Ryul Jeong at Chungnam National University in Korea.
This work was supported by the DOE Office of Science Basic Energy Science, Materials Science Engineering Division.
Illinois Grainger Engineering Affiliations
Axel Hoffmann is an Illinois Grainger Engineering professor of materials science and engineering in the Department of Materials Science and Engineering. He is also affiliated with the Materials Research Laboratory and directs the Illinois Materials Research Science and Engineering Center (I-MRSEC). He holds a Founder Professor appointment.