Accessing Higher Order Correlations in Quantum Optical States by Time Multiplexing

We experimentally measured higher order normalized correlation functions (NCF) of pulsed light with a time-multiplexing detector. We demonstrate excellent performance of our device by verifying unity valued NCF up to the eighth order for coherent light and factorial dependence of the NCF for pseudothermal light. We applied our measurement technique to a type-II parametric down-conversion source to investigate mutual two-mode correlation properties and ascertain nonclassicality.

Figure 1

Spatial mode multiport: beam splitter cascade mixing signal input with vacuum at each beam splitter.

Figure 2

Time mode multiport: experiment for correlation measurements of coherent and chaotic states by a TMD. For abbreviations, see text.

Figure 3

(a) Experimental setup for mutual correlation measurements. (b) shows the dependency of mutual correlations $g^{(n,m)}$ in theory (solid line) and measurement (squares) for five different $⟨\widehat{\mathbf{n}}⟩$. (c) displays $g^{(2)}$ of the idler beam constrained on an APD click in the signal beam, hence demonstrating the fidelity of heralding a single photon state.