Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Advanced Quantum Technologies

Dead‐Zone‐Free NMOR Atomic Magnetometer Based on Excitation of Dual‐Axis Magnetic Pulse

Liwei Jiang, Changhao Zhang, Xin Hui Zhao, Jiali Liu, Zhenglong Lu, Jianli Li

Published Jan 17, 2025• 8 citations
Publisher

Abstract

Abstract Nonlinear magneto‐optical rotation (NMOR) atomic magnetometer has extreme precision and sensitivity. However, atomic magnetometer suffers from the problem of dead zone that the sensitive signal decays to zero if the magnetic field is along some specific directions relative to the sensor. In this paper, a new scheme based on excitation of dual‐axis magnetic pulse is presented to eliminate the dead zone of NMOR atomic magnetometer. The magnetic field measurement is based on the mode of free induction decay (FID), which allows pumping and detecting stages to be separated without interference from magnetic pulse. The dead zone model is developed for NMOR atomic magnetometer from the mechanism of interaction between optical field and polarized atoms. To eliminate the dead zone of NMOR atomic magnetometer, the response model with dual‐axis magnetic pulse excitation is established by using the density matrix theory for bias magnetic field in arbitrary direction. Then the proposed method of suppressing the dead zone is examined in the experiment, which is in agreement with the developed model. The results show that the method can effectively eliminate the dead zone of NMOR atomic magnetometer, which is of great significance to measurement of magnetic field in complex magnetic environment with variable direction.

DOI
10.1002/qute.202400475

Related papers

Dead-zone-free orientation-based pulsed atomic magnetometer

Jinghong Xu, Liwei Jiang, Yuntian Zou +6 more

The dead zones of atomic magnetometers bring great challenges for the mobile applications in high-sensitivity magnetic field measurement. To solve this fundamental problem, we present a dead-zone-free orientation-based atomic magnetometer employing free-induction-decay (FID) scheme. A modulation scheme combining synchronous optical pumping and radio frequency pulse manipulation is utilized to achieve the free precession of spin polarization in all magnetic field orientations, and the FID signals are detected in two directions with an orthogonal pump-probe light configuration. We perform a comprehensive theoretical analysis of spin polarization evolution for arbitrary magnetic field orientations, and both simulation and experimental results demonstrate that the fusion of information from the pump and probe beams enables the dead-zone-free measurement of the magnetometer, with the sensor exhibiting a sensitivity in the range of 0.6 – 1.4 pT / Hz 1 / 2 across all directions. The proposed scheme is of great significance for the advancement of pulsed atomic magnetometers and their various applications in mobile platforms.

Physical Review Research•Apr 6, 2026•0 citations

Dead-zone-free single-beam atomic magnetometer based on free-induction-decay of Rb atoms

Shrey Mehta, G. K. Samanta, Raghwinder Singh Grewal

Free-induction-decay (FID) magnetometers have evolved as simple magnetic sensors for sensitive detection of unknown magnetic fields. However, these magnetometers suffer from a fundamental problem known as a “dead zone,” making them insensitive to certain magnetic field directions. Here, we demonstrate a simple experimental scheme for the dead-zone-free operation of a FID atomic magnetometer. Using a single laser beam containing equal strength of linear- and circular-polarization components and amplitude modulation at a low-duty cycle, we have synchronously pumped the rubidium (87Rb) atoms with both first- and second-order frequency harmonics. Such a pumping scheme has enabled us to observe the free Larmor precession of atomic spins at a frequency of ΩL (orientation) and/or 2ΩL (alignment) in a single FID signal, depending on the direction of the external magnetic field. We observed that the amplitude of the FID signal does not go to zero for any magnetic field direction, proving the absence of dead zones in the magnetometer. The magnetometer has a sensitivity in the range of 3.2–8.4 pT/Hz in all directions. Our experimental scheme can be crucial in developing miniaturized atomic magnetometers for various practical applications, including geomagnetic applications.

arXiv:2410.15663•Applied Physics Letters•Jan 27, 2025•8 citations

Polarization-gradient optical pumping in an atomic magnetometer

Xiaona Liu, Yujie Sun, Zhaoying Wang

High-precision Mz/Mx atomic magnetometers have “dead zones”, where the magnetic-field information will be lost because the light–atom interaction vanishes at specific field angles. To suppress dead zones, we propose a scheme with polarization-gradient optical pumping field by using counter-propagating lin⊥lin beams. We found through experiments that the lin⊥lin scheme eliminates dead zones in the transverse plane of the probe beam propagation (minimum ∼40% normalized signal) but leaves two noncanonical magic-angle-like directions (≈30 ∘ and 150 ∘ ) in the longitudinal plane, which is distinct from the standard tensor magic angle (≈54 ∘ and 126 ∘ ). These observations are quantitatively explained using a multipole-based model formulated in terms of an effective, spatially averaged density matrix, which is the first time that the spatial average density matrix has been used for energy state analysis in atomic magnetometers. Under the probing of a linearly polarized light, the measured signal is determined by the field-angle-dependent projection of the atomic longitudinal alignment moment ( m 2,0 ) onto the B 0 -defined quantization axis. Compared with other dead-zone elimination schemes, our scheme avoids polarization modulation and multi-cell architectures, showing potential for improving the spatial response range of compact atomic magnetometry.

Optics Letters•Apr 28, 2026•0 citations

Dead-zone-free free-induction-decay alkali-metal atomic magnetometer

X.-K. Wang, J. He, HH Deng +2 more

The detection dead zone is an important systematic limitation in scalar atomic magnetometers, constraining their practical utility. In this work, we demonstrate a sensitive dead zone free scalar magnetometer by integrating previously established techniques into a FID magnetometer based on Bell Bloom optical pumping. The dead zone is eliminated by inserting a reflecting mirror within a multipass cavity assisted atomic cell, which folds the optical beam into orthogonal paths. Our analysis reveals that interregion cross talk is essential for interpreting the resulted experimental signals. The sensor exhibits oscillation signal amplitude variations within a factor of three across all orientations in three dimensional space, and a field sensitivity better than 80 fT/Hz^(1/2) over the full space. We further characterize the heading error in the geomagnetic field range, where experimental results agree with theoretical predictions within 0.7 nT. Additionally, the sensor can operate in a closed loop mode by feeding back the real time frequency extracted from the FID signal to modulate the pump beam, we characterize the magnetic field slew rate of the sensor. This work paves the way towards a sensitive vector FID magnetometer.

arXiv:2609.04847•Physical Review A•Aug 25, 2026•0 citations

Free-induction-decay magnetometer based on synchronous optical pumping and RF pulse modulation

Jinghong Xu, Liwei Jiang, Junhao Liu +7 more

Free-induction-decay (FID) magnetometer is highly suitable for precise magnetic field sensing in unshielded environments with the benefit of exceptional accuracy and large dynamic range. The sensitivity of the FID magnetometer is directly influenced by the signal-to-noise ratio, making it critical to enhance the amplitude of the FID signal. In this study, we propose a FID magnetometer based on synchronous optical pumping and RF pulse modulation. A comprehensive theoretical description of the magnetometer is introduced, followed by simulation and experiment that compare the proposed modulation method with the synchronous optical pumping modulation method and the RF pulse modulation method. The results show that the synchronous optical pumping and RF pulse modulation achieves the enhancement of the FID signal and improves the magnetometer sensitivity. Furthermore, the dead zone of the magnetometer is reduced to the direction of the probe beam. This work is significant for further development of optically pumped magnetometers and provides a new scheme for their applications in unshielded environments.

EPJ Quantum Technology•May 30, 2025•10 citations

Identification and Manipulation of Atomic Polarization Moments for Nonlinear Magneto‐Optical Rotation Atomic Magnetometers

Yanchao Chai, Liwei Jiang, Jiali Liu +6 more

Abstract Polarization moments play a crucial role in measuring magnetic fields for nonlinear magneto‐optical rotation (NMOR) atomic magnetometers. However, it is challenging to distinguish between each polarization moment and evaluate its effect on the magnetic resonance response signal in an alkali vapor cell with buffer gas. To address this issue, a method is proposed to identify different polarization moments through the frequency shift of the magnetic resonance response signal. The proportion of each polarization moment is determined, and it is demonstrated that the magnetic resonance response signal is affected by the hexadecapole moment, resulting in a frequency shift and a decrease in signal amplitude. To mitigate this effect, an approach is investigated to manipulate the polarization moments by flipping the phase of the pump light. Ultimately, a 15.19% increase in response amplitude is achieved in the simulated geomagnetic environment within the magnetic shield barrel. The theory and method presented here provide strong support for the study of the polarization moments in an alkali vapor cell with buffer gas, which potentially enhance the performance of NMOR atomic magnetometers.

Advanced Quantum Technologies•Jul 19, 2024•13 citations
Abstract Nonlinear magneto‐optical rotation (NMOR) atomic magnetometer has extreme precision and sensitivity. However, atomic magnetometer suffers from the problem of dead zone that the sensitive signal decays to zero if the magnetic field is along some specific directions relative to the sensor. In this paper, a new scheme based on excitation of dual‐axis magnetic pulse is presented to eliminate the dead zone of NMOR atomic magnetometer. The magnetic field measurement is based on the mode of free induction decay (FID), which allows pumping and detecting stages to be separated without interference from magnetic pulse. The dead zone model is developed for NMOR atomic magnetometer from the mechanism of interaction between optical field and polarized atoms. To eliminate the dead zone of NMOR atomic magnetometer, the response model with dual‐axis magnetic pulse excitation is established by using the density matrix theory for bias magnetic field in arbitrary direction. Then the proposed method of suppressing the dead zone is examined in the experiment, which is in agreement with the developed model. The results show that the method can effectively eliminate the dead zone of NMOR atomic magnetometer, which is of great significance to measurement of magnetic field in complex magnetic environment with variable direction.
The dead zones of atomic magnetometers bring great challenges for the mobile applications in high-sensitivity magnetic field measurement. To solve this fundamental problem, we present a dead-zone-free orientation-based atomic magnetometer employing free-induction-decay (FID) scheme. A modulation scheme combining synchronous optical pumping and radio frequency pulse manipulation is utilized to achieve the free precession of spin polarization in all magnetic field orientations, and the FID signals are detected in two directions with an orthogonal pump-probe light configuration. We perform a comprehensive theoretical analysis of spin polarization evolution for arbitrary magnetic field orientations, and both simulation and experimental results demonstrate that the fusion of information from the pump and probe beams enables the dead-zone-free measurement of the magnetometer, with the sensor exhibiting a sensitivity in the range of 0.6 – 1.4 pT / Hz 1 / 2 across all directions. The proposed scheme is of great significance for the advancement of pulsed atomic magnetometers and their various applications in mobile platforms.
Free-induction-decay (FID) magnetometers have evolved as simple magnetic sensors for sensitive detection of unknown magnetic fields. However, these magnetometers suffer from a fundamental problem known as a “dead zone,” making them insensitive to certain magnetic field directions. Here, we demonstrate a simple experimental scheme for the dead-zone-free operation of a FID atomic magnetometer. Using a single laser beam containing equal strength of linear- and circular-polarization components and amplitude modulation at a low-duty cycle, we have synchronously pumped the rubidium (87Rb) atoms with both first- and second-order frequency harmonics. Such a pumping scheme has enabled us to observe the free Larmor precession of atomic spins at a frequency of ΩL (orientation) and/or 2ΩL (alignment) in a single FID signal, depending on the direction of the external magnetic field. We observed that the amplitude of the FID signal does not go to zero for any magnetic field direction, proving the absence of dead zones in the magnetometer. The magnetometer has a sensitivity in the range of 3.2–8.4 pT/Hz in all directions. Our experimental scheme can be crucial in developing miniaturized atomic magnetometers for various practical applications, including geomagnetic applications.
High-precision Mz/Mx atomic magnetometers have “dead zones”, where the magnetic-field information will be lost because the light–atom interaction vanishes at specific field angles. To suppress dead zones, we propose a scheme with polarization-gradient optical pumping field by using counter-propagating lin⊥lin beams. We found through experiments that the lin⊥lin scheme eliminates dead zones in the transverse plane of the probe beam propagation (minimum ∼40% normalized signal) but leaves two noncanonical magic-angle-like directions (≈30 ∘ and 150 ∘ ) in the longitudinal plane, which is distinct from the standard tensor magic angle (≈54 ∘ and 126 ∘ ). These observations are quantitatively explained using a multipole-based model formulated in terms of an effective, spatially averaged density matrix, which is the first time that the spatial average density matrix has been used for energy state analysis in atomic magnetometers. Under the probing of a linearly polarized light, the measured signal is determined by the field-angle-dependent projection of the atomic longitudinal alignment moment ( m 2,0 ) onto the B 0 -defined quantization axis. Compared with other dead-zone elimination schemes, our scheme avoids polarization modulation and multi-cell architectures, showing potential for improving the spatial response range of compact atomic magnetometry.
The detection dead zone is an important systematic limitation in scalar atomic magnetometers, constraining their practical utility. In this work, we demonstrate a sensitive dead zone free scalar magnetometer by integrating previously established techniques into a FID magnetometer based on Bell Bloom optical pumping. The dead zone is eliminated by inserting a reflecting mirror within a multipass cavity assisted atomic cell, which folds the optical beam into orthogonal paths. Our analysis reveals that interregion cross talk is essential for interpreting the resulted experimental signals. The sensor exhibits oscillation signal amplitude variations within a factor of three across all orientations in three dimensional space, and a field sensitivity better than 80 fT/Hz^(1/2) over the full space. We further characterize the heading error in the geomagnetic field range, where experimental results agree with theoretical predictions within 0.7 nT. Additionally, the sensor can operate in a closed loop mode by feeding back the real time frequency extracted from the FID signal to modulate the pump beam, we characterize the magnetic field slew rate of the sensor. This work paves the way towards a sensitive vector FID magnetometer.
Free-induction-decay (FID) magnetometer is highly suitable for precise magnetic field sensing in unshielded environments with the benefit of exceptional accuracy and large dynamic range. The sensitivity of the FID magnetometer is directly influenced by the signal-to-noise ratio, making it critical to enhance the amplitude of the FID signal. In this study, we propose a FID magnetometer based on synchronous optical pumping and RF pulse modulation. A comprehensive theoretical description of the magnetometer is introduced, followed by simulation and experiment that compare the proposed modulation method with the synchronous optical pumping modulation method and the RF pulse modulation method. The results show that the synchronous optical pumping and RF pulse modulation achieves the enhancement of the FID signal and improves the magnetometer sensitivity. Furthermore, the dead zone of the magnetometer is reduced to the direction of the probe beam. This work is significant for further development of optically pumped magnetometers and provides a new scheme for their applications in unshielded environments.
Abstract Polarization moments play a crucial role in measuring magnetic fields for nonlinear magneto‐optical rotation (NMOR) atomic magnetometers. However, it is challenging to distinguish between each polarization moment and evaluate its effect on the magnetic resonance response signal in an alkali vapor cell with buffer gas. To address this issue, a method is proposed to identify different polarization moments through the frequency shift of the magnetic resonance response signal. The proportion of each polarization moment is determined, and it is demonstrated that the magnetic resonance response signal is affected by the hexadecapole moment, resulting in a frequency shift and a decrease in signal amplitude. To mitigate this effect, an approach is investigated to manipulate the polarization moments by flipping the phase of the pump light. Ultimately, a 15.19% increase in response amplitude is achieved in the simulated geomagnetic environment within the magnetic shield barrel. The theory and method presented here provide strong support for the study of the polarization moments in an alkali vapor cell with buffer gas, which potentially enhance the performance of NMOR atomic magnetometers.