Spectral single photons characterization using generalized Hong–Ou–Mandel interferometry

We propose new methods to characterize the spectral-temporal distribution of single photons. The presented protocols take advantage of spectral filtering, frequency entanglement between two single photons, the one of interest and a reference, followed by the generalized Hong–Ou–Mandel interferometer. The measurement of the coincidence probability in these different schemes reveals the chronocyclic Wigner distribution, the pseudo-Wigner one and the spectrogram at the single photon level.