Non-classical higher-order photon correlations from a solid-state cQED system

We use the third- and fourth-order autocorrelation functions $g^{(3)}(\tau_1,\tau_2)$ and $g^{(4)}(\tau_1,\tau_2,\tau_3)$ to detect the non-classical character of light transmitted through a photonic-crystal nanocavity containing a strongly-coupled quantum dot probed with a train of coherent light pulses. We contrast the observed values of $g^{(3)}(0,0)$ with the conventionally used $g^{(2)}(0)$ and show that in addition to being necessary for detection of two-photon states emitted by a low-intensity source, $g^{(3)}$ provides a more clear indication of the non-classical character of a light source. We also present preliminary data that demonstrates bunching in the fourth-order autocorrelation function $g^{(4)}(\tau_1,\tau_2,\tau_3)$ as the first step toward detecting three-photon states.