  A diamond nano-crystal hosting a single nitrogen vacancy (NV) center is
optically selected with a confocal scanning microscope and positioned
deterministically onto the subwavelength-diameter waist of a tapered optical
fiber (TOF) with the help of an atomic force microscope. Based on this
nano-manipulation technique we experimentally demonstrate the evanescent
coupling of single fluorescence photons emitted by a single NV-center to the
guided mode of the TOF. By comparing photon count rates of the fiber-guided and
the free-space modes and with the help of numerical FDTD simulations we
determine a lower and upper bound for the coupling efficiency of (9.5+/-0.6)%
and (10.4+/-0.7)%, respectively. Our results are a promising starting point for
future integration of single photon sources into photonic quantum networks and
applications in quantum information science.
