  In recent years, ultracold atoms have emerged as an exceptionally
controllable experimental system to investigate fundamental physics, ranging
from quantum information science to simulations of condensed matter models.
Here we go one step further and explore how cold atoms can be combined with
other quantum systems to create new quantum hybrids with tailored properties.
Coupling atomic quantum many-body states to an independently controllable
single-particle gives access to a wealth of novel physics and to completely new
detection and manipulation techniques. We report on recent experiments in which
we have for the first time deterministically placed a single ion into an atomic
Bose Einstein condensate. A trapped ion, which currently constitutes the most
pristine single particle quantum system, can be observed and manipulated at the
single particle level. In this single-particle/many-body composite quantum
system we show sympathetic cooling of the ion and observe chemical reactions of
single particles in situ.
