From Spin Wave to Superconducting Circuit: Argonne Finds One-Way Street for Quantum Information

LEMONT, Ill.--(BUSINESS WIRE)--Quantum information systems could one day shape everyday life through faster computing 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, tiny circuits that can carry microwave signals. The result is a hybrid system in which these two different ways of carrying information can work together.

Superconducting circuits, standard parts of many quantum information systems, help connect and control signals inside those systems. They send and receive microwave signals in a way that strengthens communication with other parts of the device.

Spin waves offer a different advantage. Under certain conditions, spin waves are unidirectional, meaning they naturally prefer one direction of travel over the opposite. That is useful because quantum systems often need one-way signal control to help prevent unwanted noise from leaking back into the quantum components.

At the heart of the experiment is a device built on a thin magnetic film, which provides a path for spin waves to travel. 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 is tuned to interact with the spin wave in the thin magnetic film.

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 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 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.