An atomic compass -- detecting 3D magnetic field alignment with vector vortex light

TL;DR

This paper introduces a novel method for 3D magnetic field detection using structured light and atomic clouds, enabling spatially resolved magnetic vector measurements through absorption imaging and Fourier analysis.

Contribution

It demonstrates how structured vector vortex light can encode magnetic field orientation into atomic absorption patterns, providing a spatially resolved alternative to traditional magnetometry.

Findings

Magnetic field polar angle can be deduced from absorption images.

Structured atomic spin polarisation encodes magnetic field information.

Spatial Fourier analysis extracts magnetic vector orientation.

Abstract

We describe and demonstrate how 3D magnetic field alignment can be inferred from single absorption images of an atomic cloud. While optically pumped magnetometers conventionally rely on temporal measurement of the Larmor precession of atomic dipoles, here a cold atomic vapour provides a spatial interface between vector light and external magnetic fields. Using a vector vortex beam, we inscribe structured atomic spin polarisation in a cloud of cold rubidium atoms, and record images of the resulting absorption patterns. The polar angle of an external magnetic field can be deduced with spatial Fourier analysis. This effect presents an alternative concept for detecting magnetic vector fields, and demonstrates, more generally, how introducing spatial phases between atomic energy levels can translate transient effects to the spatial domain.