Photon interference of second- and third-order correlation generated by two fluorescence sources

We demonstrate the second- and third-order temporal correlation of two independent pseudo-thermal fluorescence (FL) sources. The two distinguishable sources become indistinguishable following the delay in Feynman's path. The second- and third-order correlation demonstrates the strong bunching amplitude surrounded by variable oscillations and interfering side bands (beats). Specifically, three-photon bunching is overlapped by two-photon bunching, and further decomposed into multiple lower order correlation functions. Here, the strong interference arises from source and path indistinguishable terms (varying time offset, laser frequency and the bandwidth of FL sources); The support for this idea comes from Feynman's path integral theory and sub wavelength interference for such kind of sources with appropriate detection schemes. Such phenomena may serve as modulation and carrier for quantum communication channels. (paper)