Nonlinear Faraday Rotation and Superposition-State Detection in Cold Atoms

TL;DR

This paper reports the first observation of nonlinear Faraday rotation in cold atoms at ~100 μK, demonstrating a method for creating and detecting atomic superposition states with potential for high-resolution magnetometry.

Contribution

It introduces the first observation of nonlinear Faraday rotation in cold atoms and demonstrates a new technique for superposition-state detection and control.

Findings

Nonlinear Faraday rotation up to 0.1 rad observed

Rotation results from long-lived ground-state coherence

Potential for high-resolution precision magnetometry

Abstract

We report on the first observation of nonlinear Faraday rotation with cold atoms at a temperature of ~100 uK. The observed nonlinear rotation of the light polarization plane is up to 0.1 rad over the 1 mm size atomic cloud in approximately 10 mG magnetic field. The nonlinearity of rotation results from long-lived coherence of ground-state Zeeman sublevels created by a near-resonant light. The method allows for creation, detection and control of atomic superposition states. It also allows applications for precision magnetometry with high spatial and temporal resolution.