We investigate the freezing and sudden transition in the dynamical behavior of quantum and classical correlations in a system composed of two identical non-interacting qubits locally subjected to their own non-equilibrium environments. In contrast to the equilibrium case, one can observe striking results when a bipartite quantum system couples with the non-equilibrium dephasing environment with non-stationary and non-Markovian features. Remarkably, the finite time interval in which the quantum correlation remains impervious to decoherence can be further prolonged as the environment deviates from equilibrium. This reveals that the non-equilibrium parameter provides an alternative tool to efficiently control the appearance of a sudden transition in the decay rates of correlations and their immunity towards the decoherence. Furthermore, for certain initial states, the appearance of another time-interval over which quantum correlation remains constant and the revival of classical correlation not only depends on the non-Markovianity but also on the non-equilibrium parameter.

PACS 73.20.Mf -Collective excitations (including excitons, polarons, plasmons and other charge-density excitations) PACS 32.80.Qk -Coherent control of atomic interactions with photons PACS 78.68.+m -Optical properties of surfaces Abstract -Surface plasmon polaritons (SPPs) at the interfaces of composite media have some important properties not found in conventional SPPs, i.e., SPPs at metal-dielectric interfaces. We present a useful scheme to control basic features of SPPs at the interface between a tripod-type atomic system and a silver-silica (AgSiO2) composite film. There is some interaction between the SPPs at the interface and localized surface plasmons (LSPs) due to Ag-nanoparticles in the composite. We show that the SPP's dispersive properties are strongly dependent on the coherent driving fields applied in the atomic system. Similarly, the filling ratio of the nanoparticles in the composite and the incident wavelength also affect different features of the SPPs. Our model provides more degrees of freedom for tuning the fundamental properties of SPPs at the interfaces associated with composite media.

We consider the dynamics of an array of mutually interacting cavities, each containing an ensemble of N two-level atoms. By exploring the possibilities offered by ensembles of various dimensions and a range of atom-light and photon-hopping values, we investigate the generation of multi-site entanglement, as well as the performance of excitation transfer across the array resulting from the competition between on-site non-linearities of the matter-light interaction and inter-site photon hopping. In particular, for a three cavities interacting system it is observed that the initial excitation in the first cavity completely transfers to the ensemble in the third cavity through the hopping of photons between the adjacent cavities. Probabilities of the transfer of excitation of the cavity modes and ensembles exhibit characteristics of fast and slow oscillations governed by coupling and hopping parameters respectively. In the large hopping case, by seeding an initial excitation in the cavity at the center of the array, a tripartite W state, as well as a bipartite maximally entangled state is obtained, depending on the interaction time. Population of the ensemble in a cavity has a positive impact on the rate of excitation-transfer between the ensembles and their local cavity modes. In particular, for ensembles of 5 to 7 atoms, tripartite W states can be produced even when the hopping rate is comparable to the cavity-atom one. A similar behavior of the transfer of excitation is observed for a four coupled-cavity system with two initial excitations.

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