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arXiv:2606.07899

All-Optical Wide-Field Magnetometry with Van Der Waals Quantum Sensor

Feifei Zhou, Peiyan Ma, Jiajun Li, Ke Jing, Shihao Ru, Hongwei Chen, Ying Dong, Xinqing Wang

quant-phSubmitted Jun 5, 2026• Announced Jun 9, 2026
arXivHTMLPDF

Abstract

Negatively charged boron vacancy ($V_B^-$) centers in hexagonal boron nitride ($h$-BN) have attracted wide-range interests owing to their van der Waals lattice and their potentials for $in$-$situ$ quantum sensing. Here we propose and experimentally demonstrate an all-optical strategy for wide-field magnetometry based on $V_B^-$ centers. This strategy exploits the magnetically sensitive ground-state level anti-crossing (GSLAC) of $V_B^-$ centers, which induces a strong electron spin transition between $m_S = 0$ and $m_S = -1$ states, enabling microwave-free magnetic field measurement. By monitoring the shift of GSLAC feature, the external magnetic field can be precisely determined. Using this technique, we demonstrate all-optical wide-field imaging of near-field DC magnetic field distribution from current-carrying circuits over an area of around 42 $\times$ 21 $μ$m$^2$. An estimated photon shot-noise-limited sensitivity of 67.1 $μ$T/$\sqrt{\text{Hz}}$ is achieved for a single pixel, which is an approximately threefold improvement over the ODMR method, along with a spatial resolution of about 1 $μ$m per pixel. Our approach expands the applicability of $V_B^-$ centers in quantum sensing, paving the way for robust and convenient magnetometry under extreme conditions.

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Negatively charged boron vacancy ($\mathrm{V_B^-}$) in hexagonal boron nitride (hBN) is the most extensively studied room-temperature quantum spin system in two-dimensional (2D) materials. Nevertheless, the current effective readout of $\mathrm{V_B^-}$ spin states is carried out by systematically optical methods. This limits their exploitation in compact and miniaturized quantum devices, which would otherwise hold substantial promise to address quantum sensing and quantum information tasks. In this study, we demonstrated a photoelectric spin readout technique for $\mathrm{V_B^-}$ spins in hBN. The observed photocurrent signals stem from the spin-dependent ionization dynamics of boron vacancies, mediated by spin-dependent non-radiative transitions to a metastable state. We further extend this electrical detection technique to enable the readout of dynamical decoupling sequences, including the Carr-Purcell-Meiboom-Gill (CPMG) protocols, and of nuclear spins via electron-nuclear double resonance. These results provide a pathway toward on-chip integration and real-field exploitation of quantum functionalities based on 2D material platforms.

quant-pharXiv:2511.08874•Nov 13, 2025
Negatively charged boron vacancy (VB−V_B^-VB−​) centers in hexagonal boron nitride (hhh-BN) have attracted wide-range interests owing to their van der Waals lattice and their potentials for ininin-situsitusitu quantum sensing. Here we propose and experimentally demonstrate an all-optical strategy for wide-field magnetometry based on VB−V_B^-VB−​ centers. This strategy exploits the magnetically sensitive ground-state level anti-crossing (GSLAC) of VB−V_B^-VB−​ centers, which induces a strong electron spin transition between mS=0m_S = 0mS​=0 and mS=−1m_S = -1mS​=−1 states, enabling microwave-free magnetic field measurement. By monitoring the shift of GSLAC feature, the external magnetic field can be precisely determined. Using this technique, we demonstrate all-optical wide-field imaging of near-field DC magnetic field distribution from current-carrying circuits over an area of around 42 ×\times× 21 μμμm2^22. An estimated photon shot-noise-limited sensitivity of 67.1 μμμT/Hz\sqrt{\text{Hz}}Hz​ is achieved for a single pixel, which is an approximately threefold improvement over the ODMR method, along with a spatial resolution of about 1 μμμm per pixel. Our approach expands the applicability of VB−V_B^-VB−​ centers in quantum sensing, paving the way for robust and convenient magnetometry under extreme conditions.
Recent developments in magnetic field sensing with negatively charged nitrogen-vacancy centers (NV) in diamond employ magnetic-field (MF) dependent features in the photoluminescence (PL) and eliminate the need for microwaves (MW). Here, we study two approaches towards improving the magnetometric sensitivity using the ground-state level anti-crossing (GSLAC) feature of the NV center at a background MF of 102.4 mT. Following the first approach, we investigate the feature parameters for precise alignment in a dilute diamond sample; the second approach extends the sensing protocol into absorption via detection of the GSLAC in the diamond transmission of a 1042nm laser beam. This leads to an increase of GSLAC contrast and results in a magnetometer with a sensitivity of 0.45 nT/√Hz and a photon shot-noise limited sensitivity of 12.2 pT/√Hz.
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.
Quantum sensors harness the high sensitivity of quantum systems to external perturbations to accurately measure various physical quantities. Among the quantum systems employed for sensing purposes, the nitrogen-vacancy (NV) defect in diamond has garnered considerable attention as a magnetometer. A single NV center can be integrated in a scanning probe microscope to build a highly sensitive imaging tool which is particularly adapted to the investigation of antiferromagnets. Two approaches are possible, either the measurement of small static stray fields or the detection of magnetic noise.For canted antiferromagnetic textures, like the cycloidal state in multiferroic bismuth ferrite, the NV center can probe the stray field produced by the uncompensated moments, revealing the presence of topological defects in the magnetic order at the surface of bulk single crystals [1].Alternatively, thermally activated spin waves confined in domain walls generate a magnetic noise to which the NV center is also sensitive. This property allows the localization of the domain walls, which was demonstrated in synthetic antiferromagnets [2].Besides the NV centers, new sensors are emerging as magnetic field probes like the boron vacancies in h-BN, which offer the possibilty to integrate a sensing layer inside a van der Waals heterostructure [3].[1] Finco et al., Physical Review Letters, 128, 187201 (2022)[2] Finco et al., Nature Communications 12, 767 (2021)[3] Kumar et al., Physical Review Applied, 18, L061002 (2022)
The recent decade has witnessed exciting developments in quantum science and technology. Quantum sensing is a rapidly growing branch, which exploits the fragility of quantum systems to detect small external signals. The extreme control at the single-atom level and the remarkably long coherence time of engineered quantum systems enable unprecedented sensitivity and precision, beating the performance of classical techniques. The nitrogen-vacancy (NV) center in diamond is one of the most promising quantum sensors. Its unique advantages have attracted considerable attention, including a long spin coherence time throughout a broad temperature range, nanoscale resolution limited by the sensor-sample distance, convenient optical control of its spin states and remarkably versatile sensing capabilities. Its properties are well studied under a bias magnetic field oriented along its quantization axis. However, its sensing capabilities in the presence of an off-axis magnetic field are much less explored. My research aims to unlock the full potential of NV quantum sensor by developing new sensing modalities under a magnetic field acting perpendicular to the NV axis, and furthermore, integrating them into a scanning probe microscope. In this dissertation, I will report our progress toward building a scanning NV multimodal quantum imaging platform, which will open up exciting opportunities in measuring nanoscale phenomena. The first chapter provides an introduction to the background of quantum sensing with NV centers, followed by a discussion on its basic properties and established sensing techniques. The second and third chapters are dedicated to two experiments performed under a perpendicular magnetic field where traditional NV magnetometry based on the Zeeman effect fails. In the second chapter, I will introduce a new sensing strategy that uses the entanglement between the electron and nuclear spins to restore the magnetic field sensitivity under this unfavored condition. This allows us to sense small changes in the magnetic field angle relative to the NV axis, and to detect anisotropic magnetic noise in the local environment. In the third chapter, I will present our latest development of scanning NV electrometry, where a single NV at the apex of a diamond scanning probe images external alternating (AC) and direct (DC) electric fields with sub-100 nm resolution. In the last chapter, I will discuss our efforts on four experiments that were left unfinished. I will present the results we have achieved, analyze the challenges that we faced and propose potential solutions to overcome them.
Transferable hexagonal boron nitride (hBN) hosting negatively charged boron-vacancy (VB−^{-}−) spin defects offers a versatile platform for integrated quantum magnetometry, yet quantitative imaging of magnetic microstructures remains challenging. Here, we integrate a transferred hBN flake with a 4 μμμm-diameter permalloy (Py = Ni81{81}81Fe19{19}19) microdisk and perform spatially resolved optically detected magnetic resonance measurements at room temperature. An applied in-plane magnetic field distorts the vortex-state magnetization, generating edge-localized magnetic surface charges and pronounced stray-field signatures at opposite disk edges. By referencing each pixel to its local zero-field splitting and correcting for a residual out-of-plane bias field, we quantitatively reconstruct the out-of-plane stray-field distribution, revealing peak fields of approximately 11.2 mT. An edge-charge model reproduces the spatial distribution and amplitude of the reconstructed field, linking the ODMR response to the field-driven evolution of the vortex state. These results establish transferred hBN VB−^{-}− sensors for quantitative magnetometry of magnetic microstructures.
Negatively charged boron vacancy (VB−\mathrm{V_B^-}VB−​) in hexagonal boron nitride (hBN) is the most extensively studied room-temperature quantum spin system in two-dimensional (2D) materials. Nevertheless, the current effective readout of VB−\mathrm{V_B^-}VB−​ spin states is carried out by systematically optical methods. This limits their exploitation in compact and miniaturized quantum devices, which would otherwise hold substantial promise to address quantum sensing and quantum information tasks. In this study, we demonstrated a photoelectric spin readout technique for VB−\mathrm{V_B^-}VB−​ spins in hBN. The observed photocurrent signals stem from the spin-dependent ionization dynamics of boron vacancies, mediated by spin-dependent non-radiative transitions to a metastable state. We further extend this electrical detection technique to enable the readout of dynamical decoupling sequences, including the Carr-Purcell-Meiboom-Gill (CPMG) protocols, and of nuclear spins via electron-nuclear double resonance. These results provide a pathway toward on-chip integration and real-field exploitation of quantum functionalities based on 2D material platforms.