We have demonstrated a platform for the remote detection of AC magnetic fields utilizing a gain-driven cavity magnonics system, achieving spectral coverage from the kilohertz to the megahertz regime. In this framework, an external AC field acts as a periodic Floquet drive that modulates a gain-driven polariton state, inducing discrete Floquet sidebands that are spectrally distinct from the ambient fluctuations of the magnetic background. Consequently, the AC field characteristics are encoded into the temporal phase of the coherent polariton emission, facilitating a wireless sensing architecture that bypasses the requirement for localized physical coupling or electrical interconnects at the sensing site. These results offer a practical path for high-sensitivity, real-time remote magnetometry, moving cavity magnon systems out of the lab and into functional, real-world sensing roles.
Gui et al. (2026) studied this question.