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 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 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.
Categories: cond-mat.mes-hall physics.optics quant-ph