Generation of three-photon entangled state by quantum interference between a coherent state and parametric down-conversion

Abstract

Three-photon entangled states such as a Greenberger-Horne-Zeilinger state can be produced by mixing a weak coherent state with parametric down-conversion. Quantum interference between the two states is responsible for the cancellation of unwanted photon states. Two schemes of interference are considered and both are shown to produce the entangled state.