Minimization of ion micromotion using ultracold atomic probes

We report on a sensitive method to minimize excess micromotion of an ion in a Paul trap. The ion is placed in an ultracold cloud of neutral Rb atoms in which ionic micromotion induces atomic losses and heating. Micromotion is minimized by applying static electric offset fields such that both loss and heating are minimized. We achieve a compensation on the level of the most precise compensation methods to date. In contrast to these methods, our scheme is applicable even for ions that cannot be optically probed. Furthermore, it avoids the formation of temporary patch charges which are a main issue for the long-term stability of micromotion minimization.