Fig. 1. Sketch of the experimental layout. (a) Generation of paired photons and HOM interferometer; (b) four-wave mixing in a two-level system; (c) measurement of the autocorrelation of photons coming from one out-port of the HOM instrument.

Fig. 2. Experimental results. (a) Coincidence count as a function of the delay between detected photons for paired photon generation in a two-state system; (b) HOM coincidence count.

Fig. 3. Experimental results. (a) Coincidence count as a function of the delay between detected photons for Rayleigh scatters; (b) autocorrelation of Rayleigh scatters; (c) HOM coincidence count for Rayleigh scatters; (d) coincidence count for orthogonally polarized photons in the HOM device for Rayleigh scatters.

Fig. 4. Experimental results. (a) Coincidence count for orthogonally polarized photons in the HOM device; (b) autocorrelation of photons from one out-port (PMF1) of the light source.

Fig. 5. Effect of intensity superposition for orthogonal polarization. (a) Paired photons and (b) Rayleigh scatters. The red lines in square frames represent contributions of each case to g(2)(τ). (c) For input paired photons with the same polarization, the probability of two photons being injected into PMF3 simultaneously is 50%, while for orthogonal polarization photons, the probability is 25%.

Fig. 6. Experimental results. (a) Autocorrelation function of the photons from one out-port of the HOM interferometer; (b) autocorrelation function of the photons from one out-port of the HOM device with orthogonally polarized photons.