Eliminating frequency and space-time correlations in multiphoton states - art. no. 063815

Multiphoton states constructed from photon pairs generated in the process o f spontaneous parametric down-conversion possess frequency and space-time c orrelations that may carry undesired distinguishing information. It is show n that these correlations may be eliminated if certain conditions in the so urce configuration are satisfied. For the cases in which these conditions c annot be satisfied because of experimental constraints, it is shown that th e correlations may be reduced through proper choices of crystal length and pump bandwidth. The advantage of such source engineering is that it yields much higher count rates, since no photon pairs are lost by predetection spe ctral filtering.