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arXiv:2602.07926

Real-Time Magnetic Field Sensing based on Microwave Frequency Modulated Photocurrent of Nitrogen-Vacancy Centers in Diamond

Xuan-Ming Shen, Qilong Wu, Huihui Yu, Pei-Nan Ni, Qing Lou, Chao-Nan Lin, Xun Yang, Chong-Xin Shan, Yuan Zhang

quant-phSubmitted Feb 8, 2026• Announced Feb 10, 2026• Revised Feb 12, 2026 (v2)
v1 · Feb 8, 2026v2 · Feb 12, 2026
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Abstract

While photoelectric detection of magnetic resonance (PDMR) can be applied to miniaturize nitrogen-vacancy (NV) center-based quantum sensors, real demonstration of PDMR-based magnetic field sensing remains as a distinctive challenge. To tackle this challenge, in this article, we fabricate diamond samples with electrodes and microwave antenna on the surface, and realize PDMR by detecting photocurrent in picoampere range via various lock-in amplifying modes. We obtain a theoretical and experimental sensitivity 397 nT/Hz and 921 nT/Hz of magnetic field detection in DC-10 Hz range with a laser intensity and microwave frequency modulation mode, respectively, and demonstrate for the first time, a real-time tracking of alternating magnetic field with a standard deviation of 1.5 uT. Furthermore, we investigate systematically the dependence of the PDMR contrast, linewidth and the sensitivity on the laser and microwave power, and find a perfect agreement with a master equation-based theory. Thus, our results represent a critical step forward in transitioning PDMR from a spectroscopic technique to a practical sensing modality.

Comments
14 pages, 9 figures

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While photoelectric detection of magnetic resonance (PDMR) can be applied to miniaturize nitrogen-vacancy (NV) center-based quantum sensors, real demonstration of PDMR-based magnetic field sensing remains as a distinctive challenge. To tackle this challenge, in this article, we fabricate diamond samples with electrodes and microwave antenna on the surface, and realize PDMR by detecting photocurrent in picoampere range via various lock-in amplifying modes. We obtain a theoretical and experimental sensitivity 397 nT/Hz and 921 nT/Hz of magnetic field detection in DC-10 Hz range with a laser intensity and microwave frequency modulation mode, respectively, and demonstrate for the first time, a real-time tracking of alternating magnetic field with a standard deviation of 1.5 uT. Furthermore, we investigate systematically the dependence of the PDMR contrast, linewidth and the sensitivity on the laser and microwave power, and find a perfect agreement with a master equation-based theory. Thus, our results represent a critical step forward in transitioning PDMR from a spectroscopic technique to a practical sensing modality.
Electrical detection of a nitrogen-vacancy (NV) center in diamond is advantageous for developing and integrating quantum information processing devices and quantum sensors. However, the mechanism for the electrical detection of NV spins is not fully understood. In this study, we observe positive contrast in photoelectrically detected magnetic resonance (PDMR) despite the usually observed negative PDMR contrast. To discuss the sign of the PDMR contrast, we numerically analyze the dynamics of photocarrier generation by NV centers using a seven-level rate model. It is found that the sign of the PDMR contrast depends on the difference in the photocurrent generated from the excited states and the metastable state of NV centers. Furthermore, we demonstrate alternating-current (AC) magnetic field sensing using spin coherence with the PDMR technique using a phase-cycling-based noise-canceling technique to suppress the noise from a fluctuating magnetic environment. We obtained the sensitivity of AC magnetic-field of ${\sim}29{\text{nT}}/\sqrt {{\mathbf{Hz}}} $ with the PDMR technique.
Magnetometry by using NV center, a localized coherent spin consisting of a pair of nitrogen atom and atomic void, in diamond is now regarded as a promising technique due to its potential for high sensitivity and miniaturization. The primary application for NV magnetometry was realized by optically detected magnetic resonance (ODMR). There have been plenty of reports on demonstration of magnetic sensing by using ODMR1. Towards simpler and more reliable implementation of NV magnetometry, photocurrent-detected magnetic resonance2 (PDMR) is one of the key technologies to bypass the bulky confocal optics that are necessary for ODMR-based photoluminescence detection. In a PDMR scheme, meanwhile, we use photocurrent to read out the NV spin state, which necessitates laser irradiation only for photoexcitation and spin initialization. The key for high sensitivity of PDMR-based magnetometry3 is low noise to spin-dependent signal ratio. For this sake, it is essential to mitigate the unwanted spin-independent photocurrent while maximizing the PDMR signal. In this study, we employed two different laser power and time4 in the pulse sequence to improve the signal to noise ratio5. As a result, the magnetic sensitivity as high as 13 nT/Hz0.5 was achieved.
Electrical detection of nitrogen-vacancy (N-V) centers in diamond is advantageous for developing and integrating quantum information processing devices and quantum sensors and has the potential to achieve a higher collection efficiency than that of optical techniques. However, the mechanism for the electrical detection of N-V spins is not fully understood. In this study, we observe positive contrast in photocurrent detected magnetic resonance (PDMR). Note that negative PDMR contrast is usually observed. To discuss the sign of the PDMR contrast, we numerically analyze the dynamics of photocarrier generation by N-V centers using a seven-level rate model. It is found that the sign of the PDMR contrast depends on the difference in the photocurrent generated from the excited states and the metastable state of N-V centers. Furthermore, we demonstrate ac magnetic field sensing using spin coherence with the PDMR technique. ac magnetic field measurement with the PDMR technique is still challenging because the noise from a fluctuating magnetic environment is greater than the measured signal. Here, we introduce noise suppression using a phase-cycling-based noise-canceling technique. We demonstrate electrically detected ac magnetic field sensing with a sensitivity of 29 nT ${\mathrm{Hz}}^{\ensuremath{-}1/2}$. Finally, we discuss sensitivity enhancement based on the proposed model.
Abstract The photoelectric detection of nitrogen‐vacancy (NV) magnetic resonance (PDMR) in diamond, used for spin state detection and based on reading the photocurrent resulting from NV ionization, offers physical and technical advantages for the development of miniaturized and scalable quantum sensors, as well as solid‐state quantum information devices integrated with electronics. Charge exchanges between NV centers and other optoelectrically active defects in diamond are an essential part of the PDMR scheme, impacting the spin‐state control and the performances of the photoelectric readout. Through experimental characterization and modeling, processes governing the spin‐state contrast, in particular the hole carrier contribution to the photocurrent and the role of acceptor‐type defects are discussed. Such acceptor defects can act as traps for free electrons resulting from NV photoionization. Consequently, the hole current can increase at resonance, ultimately leading to an inversion of the sign of PDMR resonances, i.e. to a positive spin contrast. Based on these findings, a method to improve PDMR performances in terms of spin contrast and photoelectric detection rate by selectively ionizing low‐energy acceptor defects using a bias red illumination is proposed. This method is shown to lead to a significant improvement of the photoelectric spin detection sensitivity, important for future practical devices.
Quantum sensing of low-frequency magnetic fields using nitrogen-vacancy (NV) center ensembles has been demonstrated in multiple experiments with sensitivities as low as $\sim1pT/1 pT/1pT/\sqrt{\text{Hz}}.Todate,however,demonstrationsofhigh−frequencymagnetometryintheGHzregimewithNVdiamondareordersofmagnitudelesssensitive,abovethenT/. To date, however, demonstrations of high-frequency magnetometry in the GHz regime with NV diamond are orders of magnitude less sensitive, above the nT/.Todate,however,demonstrationsofhigh−frequencymagnetometryintheGHzregimewithNVdiamondareordersofmagnitudelesssensitive,abovethenT/\sqrt{\text{Hz}}$ level. Here we adapt for microwave frequencies techniques that have enabled high-performance, low-frequency quantum sensors. Using a custom-grown NV-enriched diamond combined with a noise cancellation scheme designed for high-frequency sensing, we demonstrate a Rabi-sequence-based magnetometer able to detect microwave fields near 2.87 GHz with a record sensitivity of 3.4 pT/Hz\sqrt{\textrm{Hz}}Hz​. We demonstrate both amplitude and phase sensing and project tunability over a 300 MHz frequency range. This result increases the viability of NV ensembles to serve as microwave circuitry imagers and near-field probes of antennas.
Developing high performance portable sensors is of significant importance for both terrestrial and satellite communications, with quantum sensors offering potential advantages in sensitivity and bandwidth. The nitrogen vacancy center in diamond is a popular quantum sensing platform for its relative simplicity and wide range of acceptable operating conditions, but suffers a limited instantaneous bandwidth due to the narrow linewidth of the spin resonance. In this work, we first present a magnetic quantum sensing scheme utilizing heterodyne mixing with strong optical and microwave driving, achieving MHz-scale instantaneous bandwidth with a sensitivity of 548  pT/Hz548 \; \text{pT/}\sqrt{\text{Hz}}548pT/Hz​ in an active diamond volume of $ 2.5\times 10^{-4} \; \text{mm}^3$ with 2×10112 \times 10^{11}2×1011 NV centers. We then demonstrate expansion of the sensing bandwidth by employing a strong magnetic gradient and many individually modulated microwave control fields, expanding the single resonance bandwidth to 48 MHz with a peak sensitivity of 8.5  nT/Hz8.5 \; \text{nT/}\sqrt{\text{Hz}}8.5nT/Hz​.