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arXiv:2606.02749

Vector Magnetometry with Broadband Microwave Fields in Nitrogen-Vacancy Centers in Diamond

Tom R. Rieckmann, Arezoo Afshar, Aaron Z. Goldberg, Lilian Childress, Stefan Scheel, Khabat Heshami

quant-phcond-mat.mes-hallSubmitted Jun 1, 2026• Announced Jun 3, 2026
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Abstract

We present a novel method for full vector magnetometry using nitrogen-vacancy (NV) centers. In contrast to conventional optically detected magnetic resonance techniques, our method employs two distinct broadband microwave pulses and measures them after transmission through the NV sensor medium, thus capturing the line splitting of the ground state triplet due to the Zeeman effect. Two orthogonally polarized microwave pulses allow resolving all magnetic field components independently by reading out differently oriented NV centers. Simulated data is analyzed using deep neural networks, whose efficacy we expect to translate very well to experiments. Our method yields sensitivities between $5~\mathrm{pT}/\sqrt{\mathrm{Hz}}$ and $100~\mathrm{pT}/\sqrt{\mathrm{Hz}}$ across different magnetic field vector components, while achieving approximately $\mathrm{nT}$ accuracy at a signal-to-noise (SNR) ratio of $70~\mathrm{dB}$. By being capable of accurately measuring magnetic fields down to $25~\mathrm{μT}$, the need for a bias field beyond Earth's magnetic field is eliminated.

Comments
11 pages, 7 figures, 2 tables

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quant-pharXiv:2610.13379•Oct 12, 2026
We present a novel method for full vector magnetometry using nitrogen-vacancy (NV) centers. In contrast to conventional optically detected magnetic resonance techniques, our method employs two distinct broadband microwave pulses and measures them after transmission through the NV sensor medium, thus capturing the line splitting of the ground state triplet due to the Zeeman effect. Two orthogonally polarized microwave pulses allow resolving all magnetic field components independently by reading out differently oriented NV centers. Simulated data is analyzed using deep neural networks, whose efficacy we expect to translate very well to experiments. Our method yields sensitivities between 5 pT/Hz5~\mathrm{pT}/\sqrt{\mathrm{Hz}}5 pT/Hz​ and 100 pT/Hz100~\mathrm{pT}/\sqrt{\mathrm{Hz}}100 pT/Hz​ across different magnetic field vector components, while achieving approximately nT\mathrm{nT}nT accuracy at a signal-to-noise (SNR) ratio of 70 dB70~\mathrm{dB}70 dB. By being capable of accurately measuring magnetic fields down to 25 μT25~\mathrm{μT}25 μT, the need for a bias field beyond Earth's magnetic field is eliminated.
Quantum sensors based on nitrogen vacancy (NV) centers in diamond have been a central topic in the sensing community for more than a decade. The extraordinary properties at room temperature of the spin system in diamond have made it one of the most prominent quantum platforms for the development of commercial quantum sensors. In particular, the sensitivity of the electronic spin in NV centers has made diamond-based magnetic sensors of special interest for their potential application in medical, industrial or navigation solutions. However, the use of these sensors for universal vector magnetometry was constrained by the need for previous knowledge on the field being measured to fully exploit their benefits. In this work, we show a method to perform unconditional vector magnetometry without the need of external information on the magnetic field, based only on the spatial arrangement of the diamond and the microwave antenna combination. While previous NV-based vector magnetometry methods require partial knowledge of the magnetic field (e.g. a calibrated bias field), we exploit the possibilities of selecting particular directions of the spins in the diamond with elliptically polarized microwave fields. We prove that our method allows to estimate both magnitude and direction of external magnetic fields without further assumptions or constraints.
Nitrogen-vacancy (N\mathrm{N}N-VVV) centers in diamond are among the best-studied quantum-based sensors for a wide range of applications. Here, we demonstrate an optical polarization-based method for full vector magnetometry using ensembles of N\mathrm{N}N-VVV centers. The anisotropy of the electric dipole moments of the N\mathrm{N}N-VVV centers enables the assignment of the different magnetic field split transitions in the optically detected magnetic resonance spectra by appropriately setting the optical polarization in the excitation and/or detection of the N\mathrm{N}N-VVV photoluminescence signal. By further employing the optical-selection rules for the driving microwave field, we show how the full vector of the investigated magnetic field can be restored without the need to apply external bias fields. We discuss different N\mathrm{N}N-VVV-center orientation implementations and limitations toward common approximations used in the N\mathrm{N}N-VVV magnetometry literature for our approach.
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.
An ensemble of nitrogen-vacancy (NV) centers in diamond is an attractive device to detect small magnetic fields. In particular, by exploiting the fact that the NV center can be aligned along one of four different axes due to ${C}_{3\ensuremath{\nu}}$ symmetry, it is possible to extract information concerning vector magnetic fields. However, in the conventional scheme, low readout contrasts of the NV centers significantly decrease the sensitivity of the vector-magnetic-field sensing. Here, we propose a way to improve the sensitivity of the vector-magnetic-field sensing of the NV centers using multifrequency control. Since the Zeeman energy of the NV centers depends on the direction of the axis, we can independently control the four types of NV centers using microwave pulses with different frequencies. This allows us to use every NV center for the vector field detection in parallel, which effectively increases the readout contrast. Our results pave the way to realize a practical diamond-based vector field sensor.
Nitrogen-vacancy (NV) centers in diamond are optically addressable and versatile light-matter interfaces with practical application in magnetic field sensing, offering the ability to operate at room temperature and reach sensitivities below pT/Hz\sqrt{\mathrm{Hz}}Hz​. We propose an approach to simultaneously probe all of the magnetically sensitive states using a broadband microwave field and demonstrate that it can be used to measure the external DC magnetic field strength with sensitivities on the order of 10~pT/Hz\sqrt{\mathrm{Hz}}Hz​. We develop tools for analyzing the temporal signatures in the transmitted broadband microwaves to estimate the magnetic field, comparing maximum likelihood estimation based on minimizing the Kullback-Leibler divergence to various neural network models, and both methods independently reach practical sensitivities. These results are achieved without optimizing parameters such as the bandwidth, and shape of the probing microwave field such that further improvements in sensitivity can be envisioned. Our results motivate novel implementations of NV-based magnetic sensors with the potential for vectorial magnetic field detection at 1-10 kHz update rates and improved sensitivities without requiring a bias magnetic field.
The nitrogen-vacancy (NV) color center in diamond has found applications in magnetometry across various geometrical scales. In particular, vector magnetometry using hand-held devices with low power consumption is of interest for mobile and geological applications. However, such a device requires efficient driving of the four different orientations of the NV center, thus placing demands on a broadband microwave resonator that provides a uniform and highly insensitive microwave magnetic field at the resonance frequencies of the NV centers. Here, we propose a unique planar resonator design that enables efficient driving of all four orientations of NV color centers over a 100 MHz range with only 0.5 W of microwave input power and 250 mW of laser power, allowing vector magnetic field measurements. Using the planar resonator to drive NV centers in diamond, a compact vector magnetometer was fabricated and experimentally studied. The sensitivity of the device is about 1.2 nT/Hz  {1.2\text{ nT}}/{\sqrt{\text{Hz}}}\;1.2 nT/Hz​. While this is not a record sensitivity for diamond-based magnetometers, this device occupies its own niche as a compact hand-held magnetometer.