# Experimental apparatus for overlapping a ground-state cooled ion with ultracold atoms

## TL;DR

This paper presents an experimental setup where a ground-state cooled ion is overlapped with ultracold atoms, demonstrating techniques to reduce excess micromotion and analyzing the non-equilibrium dynamics of atom-ion interactions.

## Contribution

It introduces a system for overlapping a cooled ion with ultracold atoms and details methods to minimize micromotion and study non-equilibrium energy distributions.

## Key findings

- Micromotion energy reduced to the μK regime
- Spectroscopy and compensation techniques characterized micromotion
- Energy distribution follows a power-law after collisions

## Abstract

Experimental realizations of charged ions and neutral atoms in overlapping traps are gaining increasing interest due to their wide research application ranging from chemistry at the quantum level to quantum simulations of solid-state systems. Here, we describe a system in which we overlap a single ground-state cooled ion trapped in a linear Paul trap with a cloud of ultracold atoms such that both constituents are in the $\mu$K regime. Excess micromotion (EMM) currently limits atom-ion interaction energy to the mK energy scale and above. We demonstrate spectroscopy methods and compensation techniques which characterize and reduce the ion's parasitic EMM energy to the $\mu$K regime even for ion crystals of several ions. We give a substantial review on the non-equilibrium dynamics which governs atom-ion systems. The non-equilibrium dynamics is manifested by a power-law distribution of the ion's energy. We overview the coherent and non-coherent thermometry tools which we used to characterize the ion's energy distribution after single to many atom-ion collisions.