Cold atoms probe the magnetic field near a wire

TL;DR

This paper demonstrates how cold rubidium atoms in a microscopic magnetic trap can be used to measure and analyze weak magnetic fields near a current-carrying wire, revealing periodic and spatial decay characteristics.

Contribution

It introduces a method using cold atoms to probe magnetic field variations near a wire, including the detection of periodic fields and their decay profiles.

Findings

Detected a weak magnetic field component proportional to wire current

Observed the field's periodicity with a 230 μm wavelength

Field decay matches the Bessel function K_1(2π y/λ)

Abstract

A microscopic Ioffe-Pritchard trap is formed using a straight, current-carrying wire, together with suitable auxiliary magnetic fields. By measuring the distribution of cold rubidium atoms held in this trap, we detect a weak magnetic field component $\Delta B_z$ parallel to the wire. This field is proportional to the current in the wire and is approximately periodic along the wire with period $\lambda=230 \mu$m. We find that the decrease of this field with distance from the centre of the wire is well described by the Bessel function $K_1(2\pi y/\lambda)$, as one would expect for the far field of a transversely oscillating current within the wire.