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Advanced Quantum Technologies

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

Nan Wang, Shi‐Yan Li, Xiao‐Fei Ou, Wei‐Yue Zhang, Ai‐Dong Zhu, Lin Yu

Published Dec 4, 2025• 2 citations
Publisher

Abstract

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.

DOI
10.1002/qute.202500608

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A scheme of an ultra-sensitive magnetometer in the cavity quantum electromagnonics where the intracavity microwave mode coupled to a magnonic mode via magnetic dipole interaction is proposed. It is shown that by driving both magnonic and microwave modes with external classical fields and controlling the system parameters, one can reduce the added noise of magnetic field measurement below the standard quantum limit (SQL). Surprisingly, we show that beyond the rotating wave approximation (RWA), not only the added noise can be suppressed, but also the output cavity response to the input signal can be substantially amplified in order to achieve a precise magnetic-field measurement. The sensitivity of the proposed magnetic amplifier-sensor is approximately in the order of 10−18T/Hz10^{-18}T/\sqrt{Hz}10−18T/Hz​ which is competitive compared to the current state-of-the-art magnetometers like superconducting quantum interference devices (SQUIDs) and atomic magnetometers. The advantage of the proposed sensor in comparison with the other magnetometers is its high sensitivity at room temperature and sensing in a wide range of frequency up to MHz as well as its capability to signal-response amplification.
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ABSTRACT Ground‐state cooling of mechanical resonators in cavity magnomechanical (CMM) systems is critical for quantum technologies, but is fundamentally limited by intrinsically weak magnon–phonon coupling. Conventional strong‐driving‐based coupling amplification introduces excess quantum noise, while pioneering squeezing‐assisted CMM cooling schemes rely on strong driving, using squeezing to suppress heating noise, leaving the weak‐coupling bottleneck unaddressed. Here, we propose a scheme using magnon squeezing as the core mechanism to enhance effective magnon–phonon coupling via tuning squeezing strength and phase, eliminating the need for intrinsic coupling enhancement or excessively strong driving beyond the linearization regime. Theoretical analysis shows that a red‐detuned squeezed magnon mode markedly boosts the net cooling rate, enabling ground‐state cooling at higher bath temperatures, with performance further optimized by reducing magnon dissipation. This approach amplifies magnomechanical coupling while avoiding detrimental strong‐driving effects, providing a practical, low‐noise route to efficient quantum cooling in CMM systems.