Atom–photon entanglement near a plasmonic nanostructure

We investigate the atom–photon entanglement between a four-level double V-type quantum system and a linearly polarized field near a plasmonic nanostructure in the presence of a static magnetic field. It is demonstrated that the magneto-optical effect can affect the atom–photon entanglement only when the atom is near the plasmonic nanostructure. We show that atom–photon entanglement increases when the quantum system is placed near the plasmonic nanostructure in order to modification of the spontaneous decays of the quantum system. It is demonstrated that the degree of entanglement (DEM) increases by increasing the intensity of the linearly polarized field when the quantum system is close to the surface of the plasmons. Moreover, we find that near the plasmonic nanostructure, the static magnetic field has a major role in increasing the steady-state DEM so that the DEM is completely demolished in the absence of the static magnetic field. Finally, it is shown that the atom–photon entanglement near a plasmonic nanostructure is destroyed by free space decay rate.