Dead-zone-free vector magnetometry using radio frequency Rabi oscillations in alkali vapor cell*

Optically pumped magnetometers are widely used for their high sensitivity, scalar accuracy and compact design. However, their use in vector magnetometry often requires mechanical references like, e.g., a coil system, which can be prone to drifts and machining tolerances affecting vector accuracy. Common approaches to address this involve physical rotating the magnetometer system for calibration, which can be slow and cumbersome. 

An alternate approach leverages electromagnetic fields as a reference. Previously, we demonstrated vector and scalar magnetometry by exciting Rabi oscillations between ground state hyperfine manifolds with self-calibrating microwave polarization ellipses (PEs) using ⁸⁷Rb, both with cold atoms [1] and in a hot vapor cell [2]. In our poster, I will describe our recent work on using radio frequency (RF) PEs to drive Rabi oscillations between Zeeman levels within hyperfine manifolds. Unlike hyperfine transitions, Zeeman transitions are less susceptible to spin-exchange decoherence, improving vector sensitivity. Moreover, 3D RF coil configurations enable compact packaging with fast, flexible field control, allowing real-time calibration of PEs and drift compensation. We determine the DC magnetic field direction by measuring 𝜎^± Rabi frequencies, while its magnitude comes from Larmor precession measurements, offering promising applications in geomagnetic navigation, detection of magnetic anomalies, and space exploration.

[1] T. Thiele, Y. Lin, M. O. Brown, and C. A. Regal. "Self-Calibrating Vector Atomic Magnetometry through Microwave Polarization Reconstruction." Phys. Rev. Lett. 121,15 (2018)

[2] C. Kiehl, T. S. Menon, S. Knappe, T. Thiele, and C. A. Regal, "Accurate vector optically pumped magnetometer with microwave-driven Rabi frequency measurements," Optica 12, 77 (2025)