Negatively charged nitrogen vacancy (NV−) centers in diamond have been extensively studied as high-sensitivity magnetometers, showcasing a wide range of applications. This study experimentally demonstrates a vector magnetometry scheme based on synchronous manipulation of NV− center ensembles in all crystal directions using double frequency microwaves (MWs) and multi-coupled-strip-lines (mCSL) waveguide. The application of the mCSL waveguide ensures a high degree of synchrony (99%) for manipulating NV− centers in multiple orientations in a large volume. Manipulation with double frequency MWs makes NV− centers of all four crystal directions involved, and additionally leads to an enhancement of the manipulation field. In this work, by monitoring the changes in the slope of the resonance line consisting of multi-axes NV− centers, measurement of the direction of the external field vector was demonstrated with a sensitivity of . Based on the scheme, the fluorescence signal contrast was improved by four times higher and the sensitivity to the magnetic field strength was improved by two times. The method provides a more practical way of achieving vector sensors based on NV− center ensembles in diamond.
High-Q resonators with a large uniform field are widely used in magnetic imaging, but the microwave (MW) frequency shifts differently because of the near-field coupling. In this study, the major factors influencing of the frequency shifts were analyzed in a confocal system with nitrogen vacancy centers. We demonstrated a frequency calibration method involving adjustments of the applied magnetic field. This technique maintained the uniformity of the MW field with robustness to system noise, without changing the MW power. The effective imaging region reached 1.3 × 1.3 mm2 with a uniformity of 92.7%. This method preserves the stable operation of spin ensembles in magnetic imaging systems.
Experimental feasibility of potential quantum sensing and computing applications based on the oxygen-vacancy defect (VBON center) in cubic boron nitride (c-BN) is theoretically predicted by means of first-principles calculations. The proposed VBON center consisting of a boron vacancy (VB) and an adjacent substitutional oxygen (ON) is a plausible qubit candidate, which is isoelectronic to the NV− center in diamond. We found that the neutral paramagnetic VBON center is spin-triplet and exists mainly in p-type c-BN. The results demonstrate that the zero-field splitting of the neutral VBON center in the ground state falls within the microwave range and has a value of approximately 2980 MHz. Furthermore, the neutral VBON center hyperfine interactions in the ground state are determined to be in the tens of MHz. It is anticipated that our results will pave the way for the neutral VBON center acting as a scalable platform for implementing quantum information processing, sensing, and beyond.
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