Two-color photon correlations of the light scattered by a quantum dot

Abstract

Two-color second-order correlations of the light scattered near-resonantly by a quantum dot were measured by means of spectrally filtered coincidence detection. The effects of filter frequency and bandwidth were studied under monochromatic laser excitation, and a complete two-photon spectrum was reconstructed. The two-photon spectrum exhibits a rich structure associated with both real and virtual two-photon transitions down the ``dressed states'' ladder. Photon pairs generated via virtual transitions are found to violate the Cauchy-Schwarz inequality by a factor of 60. Our experiments are well described by the theoretical expressions obtained by del Valle et al. [Phys. Rev. Lett. 109, 183601 (2012)] via time- and normally-ordered correlation functions.