Generation of remote multi-photon entangled state from Einstein–Podolsky–Rosen photon pairs

We describe a protocol for generation of remote multi-photon entanglement using Einstein–Podolsky–Rosen (EPR) photon pairs via entanglement swapping. According to the requests of users, Quantum Switch (QS) can prepare three-photon W entangled states or Greenberger–Horne–Zeilinger (GHZ) states based on independent, spatially separated EPR pairs among three distant users. Only Bell states measurement (BSM) is needed utilizing a CPHASE gate and PAs. This protocol can also generate remote N-photon GHZ entangled states.