Cavity-assisted generation of entangled photons from a V-type three-level system

We propose a new type of entangled-photon generation from a V-type system in a microcavity. In contrast to the entangled-photon generation until now, all four Bell states can be freely generated from an identical cavity system by simply selecting applied-field polarizations and frequencies due to the excitation of dressed states in cavity quantum electrodynamics (CQED). CQED effects play a crucial role in providing a high degree of entanglement: (i) spectral filtering can be used to extract entangled photons due to the vacuum Rabi splitting and (ii) non-entangled co-polarized photons are strongly suppressed due to the photon blockade effect. The proposed system efficiently generates a high degree of entangled photons by moderately increasing the applied-field intensity.