  We demonstrate trapping of a single 85Rb atom at a distance of 200 nm from
the surface of a whispering-gallery-mode bottle microresonator. The atom is
trapped in an optical potential, which is created by retroreflecting a
red-detuned focused laser beam from the resonator surface. We counteract the
trap-induced light shift of the atomic transition frequency by superposing a
second laser beam with suitably chosen power and detuning. This allows us to
observe a vacuum Rabi-splitting in the excitation spectrum of the coupled
atom-resonator system. This first demonstration of stable and controlled
interaction of a single atom with a whispering-gallery-mode in the strong
coupling regime opens up the route towards the implementation of quantum
protocols and applications that harvest the chiral atom-light coupling present
in this class of resonators.
