Two-Color Photon Correlations of the Light Scattered by a Quantum Dot

TL;DR

This study investigates two-color photon correlations in light scattered by a quantum dot, revealing complex two-photon spectral structures and violations of classical inequalities, supported by theoretical models.

Contribution

It provides the first detailed measurement of two-color photon correlations in quantum dot scattering, highlighting the role of virtual transitions and their non-classical properties.

Findings

Two-photon spectrum is asymmetric with laser detuning.

Photon pairs from virtual transitions violate Cauchy-Schwartz inequality by 60 times.

Experimental results align with theoretical predictions.

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. In contrast to the ordinary one-photon spectrum, the two-photon spectrum is asymmetric with laser detuning and 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-Schwartz inequality by a factor of 60. Our experiments are well described by the theoretical expressions obtained by del Valle et al. via time-and normally-ordered correlation functions.