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Quantum technologies

Dieter Meschede's research group
Home AMO physics colloquia
  • Nathan Goldman

  • Invited speaker: Prof. Nathan Goldman
    Affiliation: Université Libre de Bruxelles
    Title: Measuring Chern Numbers with Cold Atoms: From 2D to 4D Quantum Hall Physics

    Time and room:  17:15 h, lecture hall IAP
    Abstract: In this talk, I will describe how Bloch bands with non-trivial topology can be engineered and probed in cold-atom systems. I will first briefly describe a scheme by which the topological Chern number has been extracted from a Bose gas trapped in a 2D modulated optical lattice [1]. I will then explain how this scheme can be extended to access 4D quantum Hall physics using the concept of synthetic dimensions [2]. In particular, I will present a proposal for measuring the second Chern number, an emblematic topological invariant associated with 4D Bloch bands [3].

    [1] Measuring the Chern number of Hofstadter bands with ultracold bosonic atoms, M. Aidelsburger, M. Lohse, C. Schweizer, M. Atala, J. T. Barreiro, S. Nascimbène, N. R. Cooper, I. Bloch, N. Goldman, Nature Physics 11, 162–166 (2015)
    [2] Synthetic gauge fields in synthetic dimensions, A. Celi, P. Massignan, J. Ruseckas, N. Goldman,
    I. B. Spielman, G. Juzeliunas, and M. Lewenstein, Phys. Rev. Lett. 112, 043001 (2014)
    [3] Four_Dimensional Quantum Hall Effect with Ultracold Atoms, H. M. Price, O. Zilberberg, T. Ozawa, I. Carusotto, N. Goldman, arXiv:1505.04387

  • Fabian Heidrich-Meisner

  • Invited speaker: Dr. Fabian Heidrich-Meisner
    Affiliation: LMU München
    Title: Relaxation Dynamics and Transport in the One-Dimensional Fermi-Hubbard Model

    Time and room:  17:15 h, lecture hall IAP
    Abstract: The Hubbard model harbors the key ingredients to obtain Mott-insulating behavior and antiferromagnetism and is thus a paradigmatic model for the description of strongly correlated electron systems. Besides its relevance for condensed matter systems, several experiments with ultra-cold quantum gases have realized this system using optical lattices. A major interest is in the non-equilibrium dynamics of strongly interacting closed many-body systems, aiming at an understanding of thermalization and relaxation dynamics. I will describe the relaxation dynamics in this model in the quantum quench starting from a perfect Neel state. Since a spontaneous breaking of a continuous symmetry is prohibited in one dimension, the order parameter decays to zero. Our numerical analysis unveils the characteristic time scales for the dynamics of spin- and charge-excitations and their fingerprints in the time evolution of observables. In a second part, I will turn to the discussion of transport properties. Integrable one-dimensional quantum systems are known to be prone to possess anomalous conductivities.
    We compute the thermal conductivity, show that it diverges, and discuss implications for experiments with real materials and ultracold atoms in optical lattices.

  • Enrique Solano

  • Special Colloquium

    Invited speaker: Prof. Enrique Solano
    Affiliation: University of the Basque Country, Bilbao
    Title: Quantum Simulation of the Quantum Rabi Model

    Time and room: 15:15 h, lecture hall Helmholtz-Institut für Strahlen- und Kernphysik

  • Eugene Demler

  • Invited speaker: Prof. Eugene Demler
    Affiliation: Harvard University
    Title: Nonequilibrium Quantum Dynamics: From Resonant Xray Scattering in Solids to Ultracold Atoms

    Time and room:  17:15 h, lecture hall IAP
    Abstract: Many new experimental techniques in condensed matter physics go beyond the paradigm of linear response measurements. I will use example of resonant Xray scattering in high Tc cuprates to demonstrate how new insights into experimental results can be gained by considering their nonequilibrium aspects. I will also discuss on-going experiments with ultracold atoms that can help address open problems of quantum dynamics of many-body fermionic systems.

  • Reinhard Doerner

  • Invited speaker: Prof. Reinhard Dörner
    Affiliation: Universität Frankfurt
    Title: Imaging Wave Function Of Few Body Systems: He Dimers, Trimers And The Efimov State Of He3

    Time and room:  17:15 h, lecture hall IAP
    Abstract: Two and three Helium atoms form very unusual and extreme quantum systems. Their typical extent is ten to hundred times bigger than the radius of the atoms, the wavefunction lives almost completely in the classically forbidden tunneling region and the binding energy of these systems is about 8 orders of magnitude smaller than that of a normal molecule.

    We will show how coincidence detection of charged fragments and super strong laser fields can be used to image the wave functions of these Helium quantum giants and will show the first experimental images of an Efimov state.

    Figure: A COLTRIMS Reaction Microscope

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