Science Advances (2026). DOI: 10.1126/sciadv.aee2344"> Geometry of the experiment. Credit: Science Advances (2026). DOI: 10.1126/sciadv.aee2344 Magnons are tiny waves in magnetization that travel through solid magnetic materials, much like the ripples that spread across a pond when a stone is thrown into it. Unlike photons, which travel through empty space or optical fibers, magnons propagate within a magnetic solid. Their wavelengths can be reduced to the nanometer range, meaning that magnonic circuits could, in principle, fit onto a chip no larger than those found in today's smartphones. Furthermore, as an excitation of a solid, a magnon naturally couples to numerous other fundamental quasi-particles—phonons, photons and others—making it an ideal building block for hybrid quantum systems and quantum metrology. Until now, there has been one major obstacle: magnons have had a very short lifetime.…