  Efficient self-interference of single-photons emitted by a sideband-cooled
Barium ion is demonstrated. First, the technical tools for performing efficient
coupling to the quadrupolar transition of a single $^{138}$Ba$^{+}$ ion are
presented. We show efficient Rabi oscillations of the internal state of the ion
using a highly stabilized 1.76 $\mu m$ fiber laser resonant with the
S$_{1/2}$-D$_{5/2}$ transition. We then show sideband cooling of the ion's
motional modes and use it as a means to enhance the interference contrast of
the ion with its mirror-image to up to 90%. Last, we measure the dependence of
the self-interference contrast on the mean phonon number, thereby demonstrating
the potential of the set-up for single-atom thermometry close to the motional
ground state.
