title: Spectral density matrix of a single photon measured.
abstract: We propose and demonstrate a method for measuring the spectral density matrix of a single photon pulse. The method is based on registering Hong-Ou-Mandel interference between a photon to be measured and a pair of attenuated and suitably delayed laser pulses described by a known spectral amplitude. The density matrix is retrieved from a two-dimensional interferogram of coincidence counts. The method has been implemented for a type-I down-conversion source, pumped by ultrashort laser pulses. The experimental results agree well with a theoretical model which takes into account the temporal as well as spatial effects in the source.
authors.affiliation: Institute of Physics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Toruń, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Wasilewski
authors.forename: Piotr
authors.initials: P
authors.lastname: Kolenderski
authors.forename: Robert
authors.initials: R
authors.lastname: Frankowski