Ensemble nitrogen-vacancy (NV) diamond magnetometers combine high sensitivity with vector-field reconstruction, but practical deployment is limited by errors arising from high-frequency laser noise during short-duration operations and slow-varying gain fluctuations and offset drift during long-term operation. Here, we present an integrated digital architecture for achieving NV magnetometry stability across distinct timescales. A dynamic differential readout continuously balances fluorescence and reference channels to suppress correlated laser noise. Second-derivative Lorentzian lineshape tracking enables in-situ correction of slope variations arising from slow changes in gain and optical excitation. We further identify temperature-induced bias-magnet fluctuations as a dominant source of long-term drift and introduce a magnetic eigenvector transformation that uses the intrinsic response of NV resonances to eliminate these variations. We show, under unshielded ambient conditions, that this architecture achieves an off-resonance noise factor of 1.0 $\pm$ 0.1, matching the fundamental limit with ten-fold suppression of long-term drift, enabling stable, field-ready quantum magnetometry.
Ensemble nitrogen-vacancy (NV) diamond magnetometers combine high sensitivity with vector-field reconstruction, but practical deployment is limited by errors arising from high-frequency laser noise during short-duration operations and slow-varying gain fluctuations and offset drift during long-term operation. Here, we present an integrated digital architecture for achieving NV magnetometry stability across distinct timescales. A dynamic differential readout continuously balances fluorescence and reference channels to suppress correlated laser noise. Second-derivative Lorentzian lineshape tracking enables in-situ correction of slope variations arising from slow changes in gain and optical excitation. We further identify temperature-induced bias-magnet fluctuations as a dominant source of long-term drift and introduce a magnetic eigenvector transformation that uses the intrinsic response of NV resonances to eliminate these variations. We show, under unshielded ambient conditions, that this architecture achieves an off-resonance noise factor of 1.0 ± 0.1, matching the fundamental limit with ten-fold suppression of long-term drift, enabling stable, field-ready quantum magnetometry.
Accurate measurement of vector magnetic fields is critical for applications including navigation, geoscience, and space exploration. Nitrogen-vacancy ( N V ) center spin ensembles offer a promising solution for high-sensitivity vector magnetometry, as their different orientations in the diamond lattice measure different components of the magnetic field. However, the bias magnetic field typically used to separate signals from each N V orientation introduces inaccuracy from drifts in permanent magnets or coils. Here, we present a novel bias-field-free approach that labels the N V orientations via the direction of the microwave (MW) field in a variable-pulse-duration Ramsey sequence used to manipulate the spin ensemble. Numerical simulations demonstrate the possibility to isolate each orientation’s signal with subnanotesla accuracy in most terrestrial fields, even without precise MW field calibration, at only a moderate cost to sensitivity. We also provide proof-of-principle experimental validation, observing relevant features that evolve as expected with the applied magnetic field. Looking forward, by removing a key source of drift, the proposed protocol lays the groundwork for future deployment of N V magnetometers in high-accuracy or long-duration missions.
We demonstrate an absolute magnetometer based on quantum beats in the ground state of nitrogen-vacancy centers in diamond. We show that, by eliminating the dependence of spin evolution on the zero-field splitting D, the magnetometer is immune to temperature fluctuation and strain inhomogeneity. We apply this technique to measure low-frequency magnetic field noise by using a single nitrogen-vacancy center located within 500 nm of the surface of an isotopically pure (99.99% 12C) diamond. The photon-shot-noise limited sensitivity achieves 38 nT/sqrt[Hz] for 4.45 s acquisition time, a factor of sqrt[2] better than the implementation which uses only two spin levels. For long acquisition times (>10 s), we realize up to a factor of 15 improvement in magnetic sensitivity, which demonstrates the robustness of our technique against thermal drifts. Applying our technique to nitrogen-vacancy center ensembles, we eliminate dephasing from longitudinal strain inhomogeneity, resulting in a factor of 2.3 improvement in sensitivity.
The nitrogen-vacancy (NV) center in diamond is a leading solid-state platform for room-temperature quantum magnetometry owing to its long spin coherence times, optical spin initialization and readout, and high sensitivity to magnetic, electric, and thermal perturbations. As NV-based optically detected magnetic resonance (ODMR) systems transition from controlled laboratory environments toward portable and field-deployable sensors, a detailed understanding of realistic noise sources and experimental imperfections becomes essential for optimizing performance and sensitivity. In this work, we present a comprehensive simulation framework, i.e., a digital twin, for continuous-wave wide-field ODMR in NV-center ensembles. The model is built upon a physically consistent seven-level description of the NV center and incorporates a broad range of experimentally relevant noise and imperfection mechanisms as modular, parameterized components. These include laser and microwave amplitude fluctuations, microwave phase noise, uncertainty in the NV gyromagnetic ratio, spin dephasing, temperature-induced shifts of the ground-state zero-field splitting, surface-induced magnetic field perturbations, and photon shot noise. Power broadening and contrast degradation arising from optical and microwave driving are captured self-consistently through linewidth calculations. Also, the spatial inhomogeneity is modeled via a Gaussian laser intensity profile across the sensing region...
Nitrogen-vacancy (NV) diamond magnetometry provides high sensitivity and room-temperature operation, yet its performance is limited by microwave inhomogeneity, phase noise, and nonlinear response under broadband conditions. This paper proposes a fluorescence count-rate modulation (FCM) strategy integrated with synchronized microwave control and FPGA-based timing, enabling enhanced spin manipulation efficiency, broadband phase-noise suppression, and robust sensitivity improvement. FCM introduces controlled perturbations to NV spin evolution via micro-pulse fluorescence modulation, accelerating Rabi dynamics and stabilizing optical readout. Experiments demonstrate improved coherence (6.3μs), increased contrast (52.5%), and enhanced sensitivity (6.9 nT/Hz), outperforming intensity modulation (IM), dynamic decoupling (DD), and unmodulated schemes. The method maintains stability across 100-hour continuous operation and distinct environmental conditions. Results indicate that FCM provides a scalable pathway toward practical high-precision broadband quantum magnetometry.
We demonstrate a robust, scale-factor-free vector magnetometer, which uses a closed-loop frequency-locking scheme to simultaneously track Zeeman-split resonance pairs of nitrogen-vacancy (NV) centers in diamond. This technique offers a three-orders-of-magnitude increase in dynamic range compared to open-loop methodologies; is robust against fluctuations in temperature, resonance linewidth, and contrast; and allows for simultaneous interrogation of multiple transition frequencies. By directly detecting the resonance frequencies of NV centers oriented along each of the diamond's four tetrahedral crystallographic axes, we perform full vector reconstruction of an applied magnetic field.
Nitrogen vacancy (NV) centers in diamonds have emerged as one of the most promising candidates for magnetic field sensing. However, the laser intensity fluctuation is coupled to the diamond fluorescence; thus, the sensitivity is severely affected by the noise and stability of the laser. Integrating both the diamond quantum sensor and laser noise suppression device is a crucial step toward miniaturization and practical applications. Here, we present a piezoelectric-driven device to dynamically adjust the laser noise cancelation with dimensions of 5 × 5 × 1.5 mm 3 based on a grating interferometer. This device incorporates a grating structure to produce diffracted reference light with high-accuracy intensity modulation, actively tracking the fluorescence signal for differential common-mode rejection (CMR), effectively eliminating laser noise in the system, whereby the sensitivity of magnetic field detection is increased by a factor of 34, reaching 160 pT · Hz –1/2, and beneficial to the long-term stability. The compact design of this laser noise suppressor, in combination with a miniaturized diamond magnetometer, demonstrates its potential for high-precision magnetic field detection ability and strong portability.