# Transverse optical pumping of spin states

## TL;DR

This paper introduces a novel transverse optical pumping method that uses polarization modulation to control atomic spin states in directions perpendicular to the light propagation, enhancing quantum metrology applications.

## Contribution

The study demonstrates experimentally that polarization modulation enables efficient transfer of angular momentum transversely, creating dark states and controlling spin trajectories on the Bloch sphere.

## Key findings

- Transverse optical pumping transfers angular momentum perpendicular to light propagation.
- Dark states facilitate control of spin trajectories.
- Potential improvements in quantum metrology applications.

## Abstract

Optical pumping is an efficient method for initializing and maintaining atomic spin ensembles in a well-defined quantum spin state. Standard optical-pumping methods orient the spins by transferring photonic angular momentum to spin polarization. Generally the spins are oriented along the propagation direction of the light due to selection rules of the dipole interaction. Here we present and experimentally demonstrate that by modulating the light polarization, angular momentum perpendicular to the optical axis can be transferred efficiently to cesium vapor. The transverse pumping scheme employs transversely oriented dark states, allowing for control of the trajectory of the spins on the Bloch sphere. This new mechanism is suitable and potentially beneficial for diverse applications, particularly in quantum metrology.