Entanglement generation via phase-matched processes: different Bell states within the linewidth

G. Brida, M. V. Chekhova, M. Genovese, L. A. Krivitsky

Published 2007-02-09Version 1

It is shown, theoretically and experimentally, that at any type-II spontaneous parametric down-conversion (SPDC) phase matching, the decoherence-free singlet Bell state is always present within the natural bandwidth and can be filtered out by a proper spectral selection. Instead of the frequency selection, one can perform time selection of the two-photon time amplitude at the output of a dispersive fibre. Applications to quantum communication are outlined.