arXiv subjects

Qiaochu Guo

Publications and source records attributed to Qiaochu Guo.

3 recordsLinked to original sources

arXiv2026

A Kalman Filter Based Approach to NV Diamond Data Fusion For Improved Temperature Sensing

Nitrogen-vacancy (NV) centers in diamond have been demonstrated to enable highly sensitive temperature measurements using multiple modalities. Standalone optically detected magnetic resonance (ODMR) provides robust temperature estimates, albeit with high latency, whereas all-optical measurements provide millisecond resolution but suffer from poorer long-term accuracy. In this work, we demonstrate a hot-start Kalman filtering approach that fuses the two modalities, leading to a 57% improvement in accuracy. The fused estimate achieves higher long-term accuracy with lower latency, demonstrating a viable route toward implementing self-correcting, high-precision NV-diamond temperature sensing schemes.

physics.ins-det↗

arXiv2022

Current-induced switching of thin film $α$-Fe$_2$O$_3$ devices imaged using a scanning single-spin microscope

Electrical switching of Néel order in an antiferromagnetic insulator is desirable as a basis for memory applications. Unlike electrically-driven switching of ferromagnetic order via spin-orbit torques, electrical switching of antiferromagnetic order remains poorly understood. Here we investigate the low-field magnetic properties of 30 nm thick, c-axis oriented $α$-Fe$_2$O$_3$ Hall devices using a diamond nitrogen-vacancy (NV) center scanning microscope. Using the canted moment of $α$-Fe$_2$O$_3$ as a magnetic handle on its Néel vector, we apply a saturating in-plane magnetic field to create a known initial state before letting the state relax in low field for magnetic imaging. We repeat this procedure for different in-plane orientations of the initialization field. We find that the magnetic field images are characterized by stronger magnetic textures for fields along $[\bar{1}\bar{1}20]$ and $[11\bar{2}0]$, suggesting that despite the expected 3-fold magneto-crystalline anisotropy, our $α$-Fe$_2$O$_3$ thin films have an overall in-plane uniaxial anisotropy. We also study current-induced switching of the magnetic order in $α$-Fe$_2$O$_3$. We find that the fraction of the device that switches depends on the current pulse duration, amplitude and direction relative to the initialization field. Specifically, we find that switching is most efficient when current is applied along the direction of the initialization field.

cond-mat.mtrl-sci↗

arXiv2018

Voltage driven, local, and efficient excitation of nitrogen-vacancy centers in diamond

Magnetic sensing technology has found widespread application in industries as diverse as transportation, medicine, and resource exploration. Such use cases often require highly sensitive instruments to measure the extremely small magnetic fields involved, relying on difficult to integrate Superconducting Quantum Interference Device (SQUID) and Spin-Exchange Relaxation Free (SERF) magnetometers. A potential alternative, nitrogen vacancy (NV) centers in diamond, has shown great potential as a high sensitivity and high resolution magnetic sensor capable of operating in an unshielded, room-temperature environment. Transitioning NV center based sensors into practical devices, however, is impeded by the need for high power RF excitation to manipulate them. Here we report an advance that combines two different physical phenomena to enable a highly efficient excitation of the NV centers: magnetoelastic drive of ferromagnetic resonance (FMR) and NV-magnon coupling. Our work demonstrates a new pathway to combine acoustics and magnonics that enables highly energy efficient and local excitation of NV centers without the need for any external RF excitation, and thus could lead to completely integrated, on-chip, atomic sensors.

physics.app-ph↗