Buffer gas cooling of ions in time-dependent traps using ultracold atoms

TL;DR

This paper demonstrates through simulations that buffer gas cooling with ultracold atoms can effectively cool trapped ions to near ground state energies across various trap configurations, despite micromotion effects.

Contribution

It provides a comprehensive numerical analysis showing buffer gas cooling's robustness and potential as an alternative to laser cooling for ions in diverse trap setups.

Findings

Similar ion energies achieved across different trap types.

Quantum effects do not prevent micromotion-induced heating.

Buffer gas cooling can reach near ground state, competitive with sub-Doppler methods.

Abstract

For exploration of quantum effects with hybrid atom-ion systems, reaching ultracold temperatures is the major limiting factor. In this work, we present results on numerical simulations of trapped ion buffer gas cooling using an ultracold atomic gas in a large number of experimentally realistic scenarios. We explore the suppression of micromotion-induced heating effects through optimization of trap parameters for various radio-frequency (rf) traps and rf driving schemes including linear and octupole traps, digital Paul traps, rotating traps and hybrid optical/rf traps. We find that very similar ion energies can be reached in all of them even when considering experimental imperfections that cause so-called excess micromotion. Moreover we look into a quantum description of the system and show that quantum mechanics cannot save the ion from micromotion-induced heating in an atom-ion collision. The results suggest that buffer gas cooling can be used to reach close to the ion's groundstate of motion and is even competitive when compared to some sub-Doppler cooling techniques such as Sisyphus cooling. Thus, buffer gas cooling is a viable alternative for ions that are not amenable to laser cooling, a result that may be of interest for studies into quantum chemistry and precision spectroscopy.