  We demonstrate strong coupling of single photons emitted by individual
molecules at cryogenic and ambient conditions to individual nanoparticles. We
provide images obtained both in transmission and reflection, where an
efficiency greater than 55% was achieved in converting incident narrow-band
photons to plasmon-polaritons (plasmons) of a silver nanoparticle. Our work
paves the way to spectroscopy and microscopy of nano-objects with sub-shot
noise beams of light and to triggered generation of single plasmons and
electrons in a well-controlled manner.
