Entanglement in atom-photon systems

Abstract

In this work we propose a new principle from the point of view of quantum fluctuations of observables. This new principle can be considered as an operational definition of ME states. Moreover, we show the existence of perfect entangled states of a single “spin-1” particle. We give physical examples related to the photons, and particle physics. We show that a system of 2n identical two-level atoms interacting with n cavity photons manifests entanglement and that the set of entangled states coincides with the so-called SU(2) phase states. In particular, violation of classical realism in terms of Greenberger-Horne-Zeilinger (GHZ) and Clauser-Horne-Shimoni-Holt (GHSH) conditions is proved. We also show that generation of entangled states in the atom-photon systems under consideration strongly depends on the choice of initial conditions In order to obtain maximally robust entangled states we have combined maximum principle with minimum of energy requirement for stabilization, called Mini-max principle. We discuss the generation and monitoring of durable atomic entangled state via Raman-type process, which can be used in the quantum information processing. It is shown that the system of two three-level atoms in Λ configuration in a cavity can evolve to a long-lived maximum entangled state if the Stokes photons vanish from the cavity by means of either leakage or damping. We presented some results based on the application of spherical wave representation to description of quantum properties of multipole radiation generated by atomic transitions. In particular, the angular momentum of photons including the angular momentum entanglement, the quantum phase of photons, and the spatial properties of polarization are discussed.