Inserting single Cs atoms into an ultracold Rb gas

We report on the controlled insertion of individual Cs atoms into an ultracold Rb gas at a parts per thousand 400 nK. This requires one to combine the techniques necessary for cooling, trapping and manipulating single laser cooled atoms around the Doppler temperature with an experiment to produce ultracold degenerate quantum gases. In our approach, both systems are prepared in separated traps and then combined. Our results pave the way for coherent interaction between a quantum gas and a single or few neutral atoms of another species.