  Efficient light-matter interaction lies at the heart of many emerging
technologies that seek on-chip integration of solid-state photonic systems.
Plasmonic waveguides, which guide the radiation in the form of strongly
confined surface plasmon-polariton modes, represent a promising solution to
manipulate single photons in coplanar architectures with unprecedented small
footprints. Here we demonstrate coupling of the emission from a single quantum
emitter to the channel plasmon polaritons supported by a V-groove plasmonic
waveguide. Extensive theoretical simulations enable us to determine the
position and orientation of the quantum emitter for optimum coupling.
Concomitantly with these predictions, we demonstrate experimentally that 42% of
a single nitrogen vacancy centre emission efficiently couples into the
supported modes of the V-groove. This work paves the way towards practical
realization of efficient and long distance transfer of energy for integrated
solid-state quantum systems.
