Cold-Atom Buoy: A Differential Magnetic Sensing Technique in Cold Quadrupole Traps

TL;DR

This paper introduces a differential magnetic sensing method using cold atoms in a quadrupole trap, enabling precise, common-mode noise-free magnetic field measurements with simple imaging techniques.

Contribution

The authors develop a novel differential displacement technique in cold-atom traps for vector magnetic sensing, eliminating the need for spectroscopy and enabling practical field compensation.

Findings

Achieves milli-Gauss level field resolution.

Removes common-mode effects like gravity and inhomogeneities.

Compatible with existing cold-atom setups for 3D sensing.

Abstract

We present a differential technique for vector magnetic sensing based on a cold-atom cloud in a magnetic quadrupole trap. An external homogeneous magnetic field displaces the trap center in a direction and magnitude proportional to the field. By reversing the quadrupole polarity between experimental shots and comparing the resulting cloud positions, we extract a differential displacement signal that is free from common-mode effects such as gravity and weak magnetic-field inhomogeneities. The signal is directionally proportional to the external field and requires only absorption imaging, without spectroscopic interrogation. Assuming micron-scale position resolution, the technique enables field resolution at the milli-Gauss level. It offers a practical tool for field compensation in magnetically sensitive experimental stages, bridging operational regimes from Earth-level fields to atomic magnetometry. A straightforward extension to full three-dimensional sensing is possible with only a minimal addition to standard cold-atom infrastructure.