Exponentially Enhanced Magnetic‐Field Sensing and Perfect Noise Suppression in Cavity Magnonics

ABSTRACT We propose a scheme to achieve exponential amplification of weak magnetic‐field signals and significant suppression of additional noise in a cavity magnonics. By introducing a two‐photon pump field and constructing single‐quadrature coupling between modes in the squeezed representation, a significant enhancement of the signal response based on quantum nondemolition measurement can be achieved. Fine‐tuning the squeezing parameters of the pump field enables the realization of high signal response under both strong and weak cavity‐magnon coupling regimes, thereby enhancing the controllability of the sensor. In addition, by introducing an auxiliary broadband squeezed source, the additional noise can be suppressed far below the standard quantum limit (SQL) through quantum destructive interference between the two noise fields, thereby significantly enhancing the sensor's performance. This scheme, combining exponential signal amplification with significant noise suppression, offers a powerful platform for the development of quantum sensors and advances in quantum precision measurements.