An Accurate Vector Magnetometer via Zeeman Rabi Oscillations

TL;DR

This paper presents a highly accurate, compact vector magnetometer based on Rabi oscillations in Zeeman sublevels, capable of precise magnetic field direction sensing without the need for sensor rotation or 3D optical access.

Contribution

The work introduces a novel single-axis vector magnetometer utilizing Rabi oscillations driven by RF polarization ellipses, with a calibration protocol and detailed theoretical model addressing systematics.

Findings

Achieves 80 μrad angular accuracy in vector measurements.

Demonstrates deadzone-free operation with low angular noise density.

Enables miniaturized magnetic sensors without 3D optical access.

Abstract

Accurate magnetic field direction sensing in compact platforms is critical in applications spanning magnetic navigation, space science, and biomedical imaging. We demonstrate a single-optical-axis vector optically pumped magnetometer based on Rabi oscillations between Zeeman sublevels driven by a series of resonant radiofrequency (RF) polarization ellipses (PEs). A calibration protocol based on controlled rotations of the DC magnetic field determines the spatial orientation of each PE. We develop a detailed theoretical model describing the angular dependence of the Rabi frequencies, incorporating key systematics including RF Stark shifts and Bloch-Siegert shifts. We also account for an RF-based heading-error systematic affecting Rabi-frequency measurements arising from the nonlinear Zeeman effect. Simultaneous Larmor measurements yield the magnitude of the magnetic field, enabling integrated vector-scalar measurements. The magnetometer achieves deadzone-free vector operation with 80 $\mu$rad mean angular accuracy and angular noise densities as low as 8 $\mu$rad$/\sqrt{\mathrm{Hz}}$, offering a pathway towards miniaturized sensors without requiring 3D optical access or sensor rotations.