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arXiv · 2604.27608

Quantum Magnetometry with Orientation beyond Steady-State Limits in Cavity-Magnon Systems

Zheng Liu·Ding-hui Xu·Yi-jia Yang·Yu-qiang Liu·Chang-shui Yu
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Abstract

We propose a transient vector quantum magnetometry protocol based on cavity-magnon systems. By exploiting finite-time dynamics initialized from a reservoir-engineered squeezed steady state, our scheme retains residual squeezing-induced quadrature noise reduction, which suppresses transient added noise and enhances the short-time signal-to-noise ratio beyond conventional unsqueezed steady-state limits. IQ demodulation of orthogonal cavity-output quadratures enables crosstalk-free reconstruction of all three components of a transient magnetic field, providing access to both its magnitude and orientation. This vector capability is relevant for short-lived magnetic phenomena such as pulsed spin excitations, magnetic textures, nanoscale current transients, and biomagnetic signals. In the long-time limit, we derive a closed-form stationary noise spectrum and identify the on-resonance noise-cancellation condition $g_{am}=\sqrt{\kappa_a\kappa_m}/2$ at which the cavity-added noise vanishes without strong coherent coupling. Injected squeezing further suppresses the cavity-added noise away from resonance, while an array of $N$ yttrium iron garnet spheres reduces the magnon-probe noise contribution by a factor of $1/N$. Our results establish cavity-magnon systems as a scalable platform for transient, vector-resolved quantum magnetometry.

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Zheng Liu, Ding-hui Xu, Yi-jia Yang, Yu-qiang Liu, Chang-shui Yu. 2026-04-30. Quantum Magnetometry with Orientation beyond Steady-State Limits in Cavity-Magnon Systems. https://doi.org/10.1103/z982-mv6k

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