Second-order interference of two independent photons with different spectra

Zhou Yu¹, Liu Jian-Bin^{2, 3, †}, Zheng Huai-Bin², Chen Hui², Li Fu-Li¹, Xu Zhuo²

Two-photon interference in an HOM interferometer. (a) Two photons are incident to one input port. (b) One photon is incident into one input port.