Zeeman-insensitive cooling of a single atom to its two-dimensional motional ground state in tightly focused optical tweezers

TL;DR

This paper demonstrates a method to reliably cool a single atom to its motional ground state in all three dimensions using Raman sideband cooling in optical tweezers, with high fidelity and robustness against magnetic fluctuations.

Contribution

The authors develop a robust Raman sideband cooling technique that achieves high ground state occupancy of a single atom in optical tweezers, independent of magnetic field fluctuations.

Findings

Ground state fidelity of ~0.73 in 2D radial plane

Ground state occupancy of ~0.88 for single atom realizations

3D ground state population of ~0.11

Abstract

We combine near--deterministic preparation of a single atom with Raman sideband cooling, to create a push button mechanism to prepare a single atom in the motional ground state of tightly focused optical tweezers. In the 2D radial plane, we achieve a large ground state fidelity for the entire procedure (loading and cooling) of $\sim$0.73, while the ground state occupancy is $\sim$0.88 for realizations with a single atom present. For 1D axial cooling, we attain a ground state fraction of $\sim$0.52. The combined 3D cooling provides a ground state population of $\sim$0.11. Our Raman sideband cooling variation is indifferent to magnetic field fluctuations, allowing wide--spread unshielded experimental implementations. Our work provides a pathway towards a range of coherent few body experiments.