Crossed crystal scheme for fs-pulsed entangled photon generation in   ppKTP
  We demonstrate a novel scheme for femto-second pulsed spontaneous parametric down-conversion in periodically poled KTP crystals. Our scheme is based on a crossed crystal configuration with collinear quasi-phase-matching. The non-degenerate photon pairs are split in a fiber-based wavelength division multiplexer. The source is easier to align than common pulsed sources based on bulk BBO crystals and exhibits high-quality polarization entanglement as well as non-classical interference capabilities. Hence, we expect this source to be a well-suited candidate for multi-photon state generation e.g. for linear optical quantum computation and quantum communication networks. 
Thomas Scheidl, Felix Tiefenbacher, Robert Prevedel, Fabian   Steinlechner, Rupert Ursin and Anton Zeilinger
quant-ph