Tiny magnetic waves could unlock quantum computers the size of a penny

The international research team, led by Andrii Chumak of the University of Vienna, also uncovered an important insight. They found that the lifespan of magnons is not ultimately limited by the laws of physics, but by the quality of the material they travel through. Their findings were published in Science Advances.

What Are Magnons?

Magnons are tiny waves of magnetization that move through magnetic solids. They can be compared to ripples spreading across a pond after a stone is dropped into the water. Unlike photons, which travel through empty space or optical fibers, magnons remain inside magnetic materials.

Because their wavelengths can shrink to just a few nanometers, magnon-based circuits could potentially fit onto chips no larger than those already found in smartphones. Magnons also interact naturally with other fundamental quasiparticles, including phonons and photons, making them attractive building blocks for hybrid quantum systems and quantum metrology.

Solving the Magnon Lifetime Problem

For years, one of the biggest challenges facing magnon technology has been their extremely short lifetime. Since they could survive for only a few hundred nanoseconds, they disappeared far too quickly to reliably store or transfer quantum information.

The new study changes that picture. By increasing magnon lifetimes to as much as 18 microseconds, the researchers turned these once fleeting signals into long-lasting carriers of quantum information. Their performance now approaches the timescales needed for practical quantum technologies and makes magnons comparable to the superconducting qubits used in today's leading quantum processors.

How the Researchers Achieved the Breakthrough

The breakthrough resulted from combining two important techniques.

First, instead of using conventional uniform magnons, the team generated short-wavelength magnons. These are naturally less sensitive to tiny defects on the crystal's surface, which had shortened magnon lifetimes in previous experiments.

Second, the researchers cooled ultra-pure spheres of yttrium iron garnet (YIG) to just 30 millikelvin inside a mixed-phase cryostat. At temperatures only a fraction of a degree above absolute zero, the thermal processes that normally destroy magnons are effectively frozen out.

Materials, Not Physics, Set the Limit

Perhaps the most surprising discovery was identifying what now limits magnon lifetimes.

By testing three YIG spheres with different levels of purity, the researchers found a clear pattern. The purer the crystal, the longer the magnons survived. Even the least pure sample outperformed every previous experiment.

The results suggest that future improvements depend primarily on advances in materials science rather than overcoming an unavoidable law of nature. As researchers develop even purer magnetic materials, magnon lifetimes may continue to improve.

Why This Matters for Quantum Computing

With lifetimes reaching 18 microseconds, magnons become much more than temporary signals. They could serve as reliable quantum memory devices and low-loss communication channels that move quantum information across a chip.

The researchers say magnons could eventually connect hundreds of qubits through a shared pathway, creating a long-sought "quantum bus" that would help scale future quantum computers. Because magnons naturally interact with many different quantum systems, they could also act as universal translators, allowing technologies that normally cannot communicate with one another to work together.

The study is based on experiments carried out by Rostyslav Serha during his doctoral research. The project was led by the University of Vienna in collaboration with the University of Colorado, Colorado Springs, and research institutions in Germany, the United States, and Ukraine. Coauthor Kaitlin McAllister participated through the Vienna Doctoral School in Physics, which provides internships for outstanding master's students from around the world.