Electric-field measurement in emerging power systems requires compatibility with multiple frequency bands, high field strengths, and complex electromagnetic environments. This study proposes a low-frequency AC electric-field amplitude reconstructed method based on the nitrogen-vacancy (NV) center in diamond. A Hahn–echo sequence converts the electric-field-induced quantum phase accumulation into NV fluorescence variations, and the field amplitude is retrieved through time-domain fitting and frequency-domain feature extraction. A parallel-plate electric-field generator was first calibrated using a standard electro-optic probe, followed by measurements at 2500 Hz. With the electro-optic probe result as the reference, the reconstructed electric-field amplitudes showed good quantitative agreement in the moderate-field range, with a best single-point absolute deviation of 0.0219 kV/m, while larger deviations were observed at the lower and higher ends of the tested amplitude range. By adjusting the Hahn–echo sequence to match different field periods, amplitudes at 1500 Hz and 2000 Hz were also successfully retrieved. The results demonstrate that the method is applicable to narrowband AC electric fields at known frequencies within a certain range, supporting an experimental basis for applying quantum sensing technology to power-equipment condition monitoring and measurements in complex electromagnetic environments.
Electric-field measurement in emerging power systems requires compatibility with multiple frequency bands, high field strengths, and complex electromagnetic environments. This study proposes a low-frequency AC electric-field amplitude reconstructed method based on the nitrogen-vacancy (NV) center in diamond. A Hahn–echo sequence converts the electric-field-induced quantum phase accumulation into NV fluorescence variations, and the field amplitude is retrieved through time-domain fitting and frequency-domain feature extraction. A parallel-plate electric-field generator was first calibrated using a standard electro-optic probe, followed by measurements at 2500 Hz. With the electro-optic probe result as the reference, the reconstructed electric-field amplitudes showed good quantitative agreement in the moderate-field range, with a best single-point absolute deviation of 0.0219 kV/m, while larger deviations were observed at the lower and higher ends of the tested amplitude range. By adjusting the Hahn–echo sequence to match different field periods, amplitudes at 1500 Hz and 2000 Hz were also successfully retrieved. The results demonstrate that the method is applicable to narrowband AC electric fields at known frequencies within a certain range, supporting an experimental basis for applying quantum sensing technology to power-equipment condition monitoring and measurements in complex electromagnetic environments.
Diamond nitrogen-vacancy (NV) centers are widely studied for quantum sensing in multiple physical fields due to their long coherence time and room-temperature optical readout. However, accurately decoupling and extracting signals for individual fields from fluorescence remains a major challenge. In this work, by establishing the spatial configuration between the four axes of the NV center and the directions of the externally applied electric and magnetic fields, the resonance frequency shifts of two pairs in the ODMR spectrum are exclusively induced by the electric field, whereas those of the other two pairs are exclusively induced by the magnetic field. Consequently, effective decoupling and readout of the electric field signal are realized. The experiments measure electric fields from 0 to 20 kV/cm in the diamond sample, revealing a linear relationship between the resonance frequency shift and the applied electric field, with coefficients 0.1713MHz/(kV/cm) and 0.1660MHz/(kV/cm) matching the NV center’s linear Stark effect, laying the foundation for subsequent research on electric field measurement.
Nitrogen—Vacancy (NV) center in diamond can detect tiny magnetic field due to relative long coherence time even at room temperature. Its optical accessibility and capability of thin-film formation provide us an interesting sensing modality such as wide field imaging. We have reported phase sensitive protocol for ac magnetic field designed for wide field setup.[1] In this study we demonstrate an application of phase sensitive protocol; measuring distribution of ac magnetic field strength by phase sensing. Previous methods of multi-pulse quantum sensing such as XY8 realize quite high sensitivity of ac magnetic field. Since XY8 has dependencies on strength and phase of ac magnetic field, it is necessary to adjust ac phase to an optimal point in order to obtain a best sensitivity, and we cannot distinguish the effect of amplitude and phase. Recent studies have showed utilizing time-domain information is effective for improving frequency resolution of quantum sensing,[2,3] and we found same technique is also effective for simultaneous measurement of strength and phase. Here we propose a robust method for amplitude estimation by phase sensing. We added another signal for reference, then sensing phase difference between target signal and reference can be converted into amplitude. Conventional XY8 sensing is based upon fluorescence measurement which can be affected easily by many obstacles such as stray light, autofluorescence, and fringes of excitation laser. In the other hand, our method can be more robust because it is based on phase measurement. Nothing can change the phase except absorption of ac signal. This work was supported by MEXT Q-LEAP, CAO PRISM, Japan. [1] Mizuno et al., AIP advances 2018 [2][3] Boss, Schmitt
Abstract Nitrogen-vacancy (NV) center in diamond is a promising quantum sensor with remarkably versatile sensing capabilities. While scanning NV magnetometry is well-established, NV electrometry has been so far limited to bulk diamonds. Here we demonstrate imaging external alternating (AC) and direct (DC) electric fields with a single NV at the apex of a diamond scanning tip under ambient conditions. A strong electric field screening effect is observed at low frequencies. We quantitatively measure its frequency dependence and overcome this screening by mechanically oscillating the tip for imaging DC fields. Our scanning NV electrometry achieved an AC E-field sensitivity of 26 mV μm −1 Hz −1/2 , a DC E-field gradient sensitivity of 2 V μm −2 Hz −1/2 , and sub-100 nm resolution limited by the NV-sample distance. Our work represents an important step toward building a scanning-probe-based multimodal quantum sensing platform.
High-resolution wide-spectrum measurement techniques have important applications in fields such as astronomy, wireless communication, and medical imaging. Nitrogen-vacancy (NV) center in diamond is well known for its high stability, high sensitivity, real-time monitoring, single-point detection, and suitability for long-term measurement, and has an outstanding choice for spectrum analyzers. Currently, spectrum analyzers based on NV centers as detectors can perform real-time spectrum analysis in the range of several tens of gigahertz, but their frequency resolution is limited to a MHz level. In this study, we construct a quantum diamond microwave spectrum imaging system by combining continuous wave-mixing techniques. According to the spin-related properties of the NV center in diamond, we implement optical pumping by 532 nm green laser light illuminating the diamond NV center. A spherical magnet is used to produce a magnetic field gradient along the direction of the diamond crystal. By adjusting the size and direction of the magnetic field gradient, spatial encoding of the resonance frequency of the NV center is achieved. The magnetic field gradient induces the Zeeman effect on the diamond surface at different positions, generating corresponding ODMR signals. Through accurate programming, we coordinate the frequency scanning step size of the microwave source with the camera exposure and image storage time, and synchronize them circularly according to the order of image acquisition. Ultimately, after algorithmic processing, we successfully obtain comprehensive spectrum data in a range from 900 MHz to 6.0 GHz. Within the measurable spectrum range, the system employs continuous wave-mixing, simultaneously applying resonant microwaves and slightly detuning auxiliary microwaves to effectively excite the NV center. This method triggers off microwave interference effects, disrupting the balance between laser-induced polarization and microwave-induced spontaneous relaxation. Specifically, microwave interference causes the phase and amplitude of the fluorescence signal to change, leading to the generation of alternating current fluorescence signals. This further enhances the response of the NV magnetometer to weak microwave signals. The method enables the system to achieve a frequency resolution of 1 Hz in the measurable spectrum range, and it can separately measure the frequency resolution of multiple frequency points with a frequency step size of 1 MHz. The research results indicate that the wide-spectrum measurement based on NV centers can achieve sub-hertz frequency resolution, providing robust technical support for future spectrum analysis and applications.
Characterizing electric field noise in diamond is crucial for utilizing nitrogen-vacancy (NV) centers as probes and qubits. However, NV centers under axial magnetic fields are sensitive to magnetic fields and thus are limited in their ability to characterize electric fields directly. In this study, we engineered NV centers exhibiting strong intrinsic effective electric fields through ion implantation into CVD-grown diamond. We selected seven NV centers with splittings in the range of 18–66 MHz as the focus of our research. By virtue of the suppression effect of the strong effective field on the magnetic field, the energy level shift caused by the magnetic field was reduced by two orders of magnitude. Combining spectral decomposition techniques, we extracted the electric noise spectrum in the low-frequency range from the environmental noise. Our results indicate that the near-surface electrical noise of the diamond deviates from the 1/f noise model, and two characteristic correlation times were observed within the measured frequency range (1–10 MHz).
An ensemble of nitrogen-vacancy (NV) centers in diamond is a fascinating candidate for realizing a sensitive magnetic field sensor. In particular, since the axes of the NV centers are distributed along four directions, a collection of measurement data from NV centers with different axes provides information on the vector components of a magnetic field. However, in the conventional approach, the low measurement contrast of NV centers limits the sensitivity of vector magnetic field sensing. Recently, to overcome this problem, multi-frequency control of the NV centers has been proposed. The key idea is that four types of NV centers with different axes are simultaneously controlled by multi-frequency microwave pulses. Here, we demonstrate vector magnetic field sensing with an ensemble of NV centers in diamond via such multi-frequency control with pulsed-type measurements. We use Hahn echo pulses and extract information on the vector components of an applied AC magnetic field. We find that the sensitivity of the vector field sensing with multi-frequency control is better than that with single-frequency control for every vector component of a magnetic field.