Ultrafast photon-photon interaction in a strongly coupled quantum   dot-cavity system
  We study dynamics of the interaction between two weak light beams mediated by a strongly coupled quantum dot-photonic crystal cavity system. First, we perform all optical switching of a weak continuous-wave signal with a pulsed control beam, and then perform switching between two pulsed beams (40ps pulses) at the single photon level. Our results show that the quantum dot-nanocavity system creates strong, controllable interactions at the single photon level. 
Dirk Englund, Arka Majumdar, Michal Bajcsy, Andrei Faraon, Pierre   Petroff, Jelena vuckovic
quant-ph physics.optics