Abstract Magnetic field sensors based on quantum sensing effects demonstrate significantly superior sensitivity compared to traditional sensors. Among these, diamond NV centers have emerged as the most promising quantum magnetic field sensors for practical industrial implementation at room temperature. However, current applications of diamond NV centers in power measurement face challenges due to insufficient measurement response speed. To address this challenge, this paper designs a rapid diamond NV-center magnetic field measurement system based on fast demodulation and ultrafast frequency agility. To this end, this paper employs a field-programmable gate array (FPGA) board-level device to implement signal demodulation and microwave control, thereby enabling a rapid magnetic field measurement system for diamond NV centers with fast demodulation and ultrafast frequency switching. By outputting current through a current source to a double-layer Helmholtz coil, the system generated a z-axis magnetic field. The system achieved a current measurement accuracy of 0.08% within the range of 0.5–10 A, with a static magnetic field sensitivity exceeding 8.30 nT/Hz 1 / 2 . The designed system achieves signal demodulation within less than 80 μs and frequency hopping of modulated microwave signals within less than 1 μs. Compared to benchtop systems, the measurement response speed has been improved from the second-level timescale to the millisecond-level timescale.
Abstract Magnetic field sensors based on quantum sensing effects demonstrate significantly superior sensitivity compared to traditional sensors. Among these, diamond NV centers have emerged as the most promising quantum magnetic field sensors for practical industrial implementation at room temperature. However, current applications of diamond NV centers in power measurement face challenges due to insufficient measurement response speed. To address this challenge, this paper designs a rapid diamond NV-center magnetic field measurement system based on fast demodulation and ultrafast frequency agility. To this end, this paper employs a field-programmable gate array (FPGA) board-level device to implement signal demodulation and microwave control, thereby enabling a rapid magnetic field measurement system for diamond NV centers with fast demodulation and ultrafast frequency switching. By outputting current through a current source to a double-layer Helmholtz coil, the system generated a z-axis magnetic field. The system achieved a current measurement accuracy of 0.08% within the range of 0.5–10 A, with a static magnetic field sensitivity exceeding 8.30 nT/Hz 1 / 2 . The designed system achieves signal demodulation within less than 80 μs and frequency hopping of modulated microwave signals within less than 1 μs. Compared to benchtop systems, the measurement response speed has been improved from the second-level timescale to the millisecond-level timescale.
In modern-day quantum metrology, quantum sensors are widely employed to detect weak magnetic fields or nanoscale signals. Quantum devices, exploiting quantum coherence, are inevitably connected to physical constants and can achieve accuracy, repeatability, and precision approaching fundamental limits. As a result, these sensors have shown utility in a wide range of research domains spanning both science and technology. A rapidly emerging quantum sensing platform employs atomic-scale defects in crystals. In particular, magnetometry using nitrogen-vacancy (NV) color centers in diamond has garnered increasing interest. NV systems possess a combination of remarkable properties, optical addressability, long coherence times, and biocompatibility. Sensors based on NV centers excel in spatial resolution and magnetic sensitivity. These diamond-based sensors promise comparable combination of high spatial resolution and magnetic sensitivity without cryogenic operation. The above properties of NV magnetometers promise increasingly integrated quantum measurement technology, as a result, they have been extensively developed with various protocols and find use in numerous applications spanning materials characterization, nuclear magnetic resonance (NMR), condensed matter physics, paleomagnetism, neuroscience and living systems biology, and industrial vector magnetometry. In this chapter, NV centers are explored for magnetic sensing in a number of contexts. In general, we introduce novel regimes for magnetic-field probes with NV ensembles. Specifically, NV centers are developed for sensitive magnetometers for applications where microwaves (MWs) are prohibitively invasive and operations need to be carried out under zero ambient magnetic field. The primary goal of our discussion is to improve the utility of these NV center-based magnetometers.
Abstract We developed a compact, portable quantum sensor module for pulsed measurements using diamond nitrogen-vacancy (NV) centers, an excitation laser diode of 3 mW and a microwave source of 15 dBm. This module allowed the evaluation of ensemble diamond NV centers for measuring magnetic fields by continuous wave— optically detected magnetic resonance (ODMR), Rabi oscillation, pulsed ODMR, Ramsey measurement and spin-echo measurement. The sensitivity through pulsed measurements reached 40 nT/ Hz at 1 Hz, which achieved higher sensitivity by one order, especially at a frequency around 1 Hz compared with previously reported compact modules using diamond NV centers.
Nitrogen-vacancy (NV) color centers in diamond are promising solid-state quantum sensors working at room temperature. The number of NV centers limits the magnetic sensitivity of the quantum magnetometer. Increasing the number of NV centers is a challenging task due to technical issues such as microwave power density, detection noise.Here, we developed the sensor system with a large detection volume which contains a lot of NV centers. The microwave circuit enhances microwave power density. Digital filter with frequency modulation of microwave allows us to detect the magnetic field with low noise. Consequently, we obtained a DC magnetic field sensitivity of 980 pT/√Hz.This work was supported by MEXT Quantum Leap Flagship Program (MEXT Q-LEAP) Grant Number JPMXS0118067395.
Diamond quantum sensors utilizing nitrogen-vacancy (NV) centers in diamond can measure a tiny magnetic-field variation at room temperature with a high linearity and high spatial resolution. Because of these advantages, they have been actively studied for application to measure a biomagnetic field. In biomagnetic sensing applications, it is effective to measure at multiple points simultaneously with high sensitivity. In this study, we developed a highly sensitive diamond quantum sensor that can simultaneously measure the magnetic field at two points at the millimeter interval. We used two diamonds that were split from one HPHT-grown diamond and placed them at the 3-mm interval. A laser-induced fluorescence from the two diamonds were detected by a single photodiode. We applied different bias magnetic fields to each diamond, and thus the magnetic resonances at these diamonds had different resonance frequencies. By applying microwave fields whose frequencies were modulated at different modulation frequencies, the magnetic fields at the two diamonds can be obtained independently after demodulation. The noise spectral densities in the magnetic field measurement at the two diamonds’ locations. Since the measurement was performed outside a magnetic shield, a severe low-frequency environmental noise from railways and power line (50 Hz) noise peaks were observed. We evaluated the field sensitivities at the two diamonds to be 22 pT/√Hz in 25-300 Hz range with neglecting the power-line noise peaks and the environment noise peaks. The capability of simultaneously measuring a magnetic field at two points with the such high sensitivities will facilitate the biomagnetic sensing applications.
Nitrogen-vacancy (NV) centers in diamond have emerged as a robust room-temperature solid-state platform for weak magnetic field detection. Several NV-based magnetometers have been proposed in the past decades, but they still suffer from either low sensitivity or high power consumption. This is a challenge for sensors deployed in remote locations on Earth or in space that are not connected to the power grid. Although sunlight-driven quantum magnetometry, which does not rely on conventional energy sources, has been proposed as a possible solution, its sensitivity remains a limitation. Here, we present an impressive improvement in the sensitivity of the sunlight-driven NV-diamond quantum magnetometer. A crucial aspect of our approach involves leveraging the ground-state level anti-crossing properties of the NV centers, coupled with magnetic flux concentrators. This integration enables us to achieve a magnetic-field sensitivity of 26 pT/Hz in a laboratory environment and 49 pT/Hz when the magnetometer operates outdoors under sunlight. We also illustrate the promising potential of further improving the sensitivity to the subpicotesla level by using cutting-edge technologies. Furthermore, we reveal the capability of this quantum magnetometer as a receiver of extremely low-frequency magnetic signals and pave the way for communication applications. These advancements represent a significant leap toward attaining high-sensitivity and energy-efficient magnetic field sensing and expanding the range of possible applications for these environmentally sustainable quantum technologies.
Diamond nitrogen-vacancy (NV) centers have attracted extensive research interest for quantum sensing applications across various physical domains, owing to their prolonged coherence times and the capability of optical readout at room temperature, which offers a promising technical pathway for detecting fast-responding and transient signals in emerging power systems. This work presents a quantum sensing device based on the Zeeman and Stark effects of NV centers, designed for power system measurement applications, with a rated voltage of 10kV and a rated current of 1kA, enabling simultaneous voltage and current sensing. The device achieves a measurement accuracy of 0.69% under the rated voltage of 10 kV and +0.23% under the rated current of 1 kA, verifying the feasibility of employing quantum sensing based on NV centers for simultaneous voltage and power measurements in power systems.