Nonclassical higher-order photon correlations with a quantum dot strongly coupled to a photonic-crystal nanocavity

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 nonclassical character of the light transmitted through a photonic-crystal nanocavity containing a strongly coupled quantum dot probed with a train of coherent light pulses. We contrast the value of g((3))(0,0) with the conventionally used g((2))(0) and demonstrate that, in addition to being necessary for detecting two-photon states emitted by a low-intensity source, g((3)) provides a more clear indication of the nonclassical 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.