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 weak pulsed beams (40 ps pulses). Our results show that the quantum dot-nanocavity system enables fast, controllable optical switching at the single-photon level.