Very large optical rotation generated by Rb vapor in a multi-pass cell

TL;DR

This paper demonstrates a multi-pass cell technique to generate extremely large optical rotations in Rb vapor, enabling high-sensitivity atom sensing and revealing suppressed spin relaxation in superposition states.

Contribution

It introduces the use of multi-pass cells for large Faraday rotations and shows reduced spin relaxation in superposition states, advancing quantum sensing methods.

Findings

Over 100 radians of polarization rotation observed

10-fold suppression of transverse spin relaxation

Multi-pass cells offer deterministic light passes unlike cavities

Abstract

Paramagnetic Faraday rotation is a powerful technique for atom sensing widely used in quantum non-demolition measurements, fundamental symmetry tests, and other precision measurements. We demonstrate the use of a multi-pass optical cell for Faraday rotation spectroscopy and observe polarization rotation in excess of 100 radians from spin-polarized Rb vapor. Unlike optical cavities, multi-pass cells have a deterministic number of light passes and can be used to measure large optical rotations. We also observe a 10-fold suppression of transverse spin relaxation when Rb atoms are placed in a coherent superposition state immune to spin-exchange collisions.