Minimizing rf-induced excess micromotion of a trapped ion with the help of ultracold atoms

We report on the compensation of excess micromotion due to parasitic rf-electric fields in a Paul trap. The parasitic rf-electric fields stem from the Paul trap drive but cause excess micromotion, e.g., due to imperfections in the setup of the Paul trap. We compensate these fields by applying rf-voltages of the same frequency, but adequate phases and amplitudes to Paul trap electrodes. The magnitude of micromotion is probed by studying elastic collision rates of the trapped ion with a gas of ultracold neutral atoms. Furthermore, we demonstrate that also reactive collisions can be used to quantify micromotion. We achieve compensation efficiencies of about 1 $$\,\text {Vm}^{-1}$$ , which is comparable to other conventional methods.