  Linear optics quantum logic gates are the best tool to generate multi-photon
entanglement. Simplifying a recent approach [Phys. Rev. A 65, 062324; Phys.
Rev. A 66, 024308] we were able to implement the conditional phase gate with
only one second order interference at a polarization dependent beam splitter,
thereby significantly increasing its stability. The improved quality of the
gate is evaluated by analysing its entangling capability and by performing full
process tomography. The achieved results ensure that this device is well suited
for implementation in various multi photon quantum information protocols.
