Quantum cloning and multi-photon quantum cryptography
D. Boumeester · 2005
Summary form only given. Multi-photon states from stimulated parametric down~canverrionc an be entangled both in polarization and photon number. Maximally high-dimemion entanglement can be concentrated from these states via photon-counting. We show experimental results for the concentration of a ratational symmetric four-photon entangled state obtained by stimulated emission of the familiar anti-symmetric two-particle Bell state.