Many-Body Localisation of Fermions in a 1D Quasi-Random Disordered Lattice (M. Schreiber) / Photon Transmissions in Rydberg-EIT Systems by Multi-Photon Scattering Theory (Dr. T. Shi)

  • Double Feature!
  • Date: Jul 14, 2015
  • Time: 02:30 PM - 04:00 PM (Local Time Germany)
  • Speaker: Dipl. Phys. Michael Schreiber, Abt. Quanten-Vielteilchensysteme / Dr. Tao Shi, Abt. Theorie
  • Room: Herbert Walther Lecture Hall
  • Host: MPQ
abstracs...

Many-Body Localisation of Fermions in a 1D Quasi-Random Disordered Lattice (M. Schreiber)
While Anderson localisation of non-interacting particles has been studied extensively, much less is known about localisation in interacting systems. As an experimental probe, we study in an interacting many-body system the breakdown of ergodicity and the resulting absence of thermalisation, which are some of the key features of localised systems. We have investigated the many-body localization transition for interacting ultracold fermions in a quasi-random 1D lattice by measuring the relaxation dynamics of an initial Charge Density Wave (CDW). While the CDW order quickly decays in the thermalising case, a CDW order persisting for long evolution times, reveals the breakdown of ergodicity and many-body localisation. We have characterised this phase transition and studied the influence of energy density on localisation.

Photon Transmissions in Rydberg-EIT Systems by Multi-Photon Scattering Theory (Dr. T. Shi)
We develop the scattering theory to study the multi-photon transport to the quantum emitters by using the quantum regression theorem and the path integral formalism. The transition amplitude, the S-matrix, and the generalized master equation for the emitters during the scattering processes are investigated. Here, the path integral formalism results in the exact result, which can be used to check the validity of the Born-Markov approximation used in the quantum regression theorem. By using two examples, i.e., few-photon scattering by the two-level system and the Jaynes-Cummings model, we show that how to apply the scattering theory to study the quantum statistics of the out-going photons and the transient processes of the emitters. Finally, we apply the developed scattering theory to study the few-photon transport to the Rydberg-electromagnetic induced transparency (EIT) atom array. Here, we show the interplay between EIT effect and the Rydberg interaction results in the rich photon statistics, and the propagation of the dark polaritons is studied.

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