Single Cs atoms interacting with an ultracold Rb gas

We immerse single Cs atoms into a many body systems consisting of cold and ultracold Rb gases in order to use the single Cs atom as a sensitive probe for inter-species interaction and as an agent to manipulate the quantum gas. In order to study ground state collisions between a single Cs atom and a quantum degenerate Rb gas we have developed techniques to combine a quantum gas with a single trapped neutral atom. For this purpose, an optically trapped Rb BEC is prepared in the magnetic field insensitive F=1, mF=0 state. Then single Cs atoms are loaded into a superimposed 1D-lattice, which exerts a strong potential for Cs atoms and a weak potential for Rb. At ultralow temperatures and with negligible scattering of photons, ground state collisions between the single atom and the quantum gas determine the interaction. This enables (coherent) probing and manipulation of the BEC by the single atom. We report on the ground state interactions between single Cs atoms and a quantum gas and our recent progress controlling the single atom inside the quantum gas.