Tiny Magnetic Waves Could Unlock Quantum Computers the Size of a Penny

Researchers have achieved a significant breakthrough in quantum computing by extending the lifespan of magnons, or magnetic waves, from nanoseconds to 18 microseconds. This nearly hundredfold increase in coherence time addresses a major hurdle in using magnons for stable quantum information storage and transfer. The advancement suggests that magnon-based circuits could enable ultra-compact quantum processors and efficient quantum buses to connect hundreds of qubits on a single chip.

An international research team led by Andrii Chumak at the University of Vienna has demonstrated that magnons can maintain quantum information for up to 18 microseconds, a nearly 100-fold improvement over the previous limit of a few hundred nanoseconds. By cooling ultra-pure spheres of yttrium iron garnet (YIG) to 30 millikelvin inside a mixed-phase cryostat, the team effectively froze out thermal processes that typically destroy these magnetic waves. This performance level makes magnons comparable to the superconducting qubits used in today's leading quantum processors, positioning them as viable candidates for practical quantum technologies.

The breakthrough, published in Science Advances, resulted from combining the generation of short-wavelength magnons with the use of high-purity materials. Unlike conventional uniform magnons, short-wavelength variants are naturally less sensitive to microscopic surface defects that previously shortened magnon lifetimes. The study, based on experiments by Rostyslav Serha and involving collaborators from the University of Colorado, Colorado Springs, and institutions in Germany and Ukraine, revealed that magnon longevity is limited by material purity rather than fundamental physical laws. Testing YIG spheres with varying purity levels showed that higher crystal quality directly correlates with longer lifetimes, suggesting that future advances in materials science could further extend these durations.

The implications for the quantum computing sector are substantial, particularly regarding hardware miniaturization and scalability. Because magnons have wavelengths that can shrink to a few nanometers, they could allow for quantum circuits to fit on chips no larger than those found in smartphones, potentially leading to computers the size of a penny. Beyond compact processors, these long-lived magnons could function as a quantum bus to connect hundreds of qubits or act as universal translators between disparate quantum systems that normally cannot communicate. This versatility makes them attractive building blocks for hybrid quantum systems and quantum metrology.