  We present two applications of a single nitrogen vacancy center in a
nanodiamond as quantum probe for plasmonic nanostructures. Coupling to the
nanostructures is achieved in a highly controlled manner by picking up a
pre-characterized nanocrystal with an atomic force microscope and placing it at
the desired position. Local launching of single excitations into a nanowire
with a spatial control of few nanometers is demonstrated. Further, a two
dimensional map of the electromagnetic environment of a plasmonic bowtie
antenna was derived, resembling an ultimate limit of fluorescence lifetime
nanoscopy.
