arXiv subjects

Ding-hui Xu

Publications and source records attributed to Ding-hui Xu.

3 recordsLinked to original sources

arXiv2026

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

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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arXiv2025

Enhancing optomechanical force sensing utilizing synthetic magnetism

In precision force sensing of multi-mechanical mode optomechanical systems, coherent interference can decouple certain degenerate vibrational modes from the cavity field, leading to incomplete information regarding the measured signal. In this paper, we propose a scheme to enhance and control the detection bandwidth in optomechanical force sensing by exploiting synthetic magnetism achieved through tuning phonon hopping interactions. By toggling between broken and unbroken dark mode, this approach effectively manages the response bandwidth and exhibits intriguing additional noise characteristics. Specifically, when the dark mode remains unbroken, the thermal noise is robust and reduced to half of that of a standard device. In contrast, when the dark mode is broken, thermal noise increases substantially at mechanical resonance but remains the same as when the dark mode is unbroken at effective detection frequencies. Moreover, our scheme offers the dual benefit of amplifying the mechanical response while suppressing additional noise, with the potential to surpass the standard quantum limit.

quant-ph↗

arXiv2024

Enhanced Sensing by Geometric Tuning of YIG Spheres: Noise Reduction, Signal Amplification and Directional Magnetic Field Detection

Noise suppression and directional signal enhancement are essential challenges in detecting weak magnetic fields in cavity electrodynamics systems. Traditional schemes struggle to reduce magnonic probe noise but lack directional sensing capabilities. We exploit an innovative and intrinsic squeezing mechanism by leveraging the geometric configuration of an anisotropic ellipsoidal yttrium iron garnet (YIG) sphere and its interaction with internal demagnetization fields. This mechanism can enhance magnetic field signals and suppress noise in the target direction while suppressing sensitivity in non-target directions to avoid disturbing the target direction, thus generating a directionally selective sensing scheme realizing high-precision detection in complex environments. In particular, the target-direction sensor performance can be optimized by adjusting the YIG sphere's geometry (e.g., aspect ratio) without complex setups, ensuring high feasibility and scalability. Our approach offers greater flexibility and directionality by tuning the YIG sphere's geometry than existing methods. This innovation provides a new approach for weak magnetic field detection in cavity magnonics systems, with potential applications in biomedical imaging, quantum sensing, precision measurement, and environmental monitoring.

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