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Quantum technologies

Dieter Meschede's research group
Home AMO physics colloquia
  • Bachelor and Master talks

  • 16:00 Jonathan Zopes: "Einzelplatzdetektion im optischen Gitter unterhalb des Beugungslimits"
    16:40 Thomas Gehrmann: "An Optical Stokes Polarimeter for Optimized Spin-dependent Transport of Atoms"
    17:40 Deena Kim: "Deterministic Atom Sorting in Optical Lattices"
    18:20 Christian Lützler: "Fabrication of Optical Microfibers"
    Room: lecture hall IAP

  • A. Femius Koenderink

  • Invited speaker: Prof. Dr. A. Femius Koenderink
    Affiliation: AMOLF, Amsterdam
    Title: Subwavelength Plasmonic And Magnetic Resonators To Control Photons And Emitters
    Time and room: 17:15  lecture hall IAP
    Abstract: Controlling how photons are emitted, absorbed and redirected on the nanoscale is of great interest for quantum information, microscopy and nanoscale light sources. Nanophotonics increasingly explores the solutions that electrical engineers use to control RF waves using broadband antennas, which are very different from traditional cavity QED approaches.

    We explore how plasmonic and metamaterial scatterers allow to transpose RF antenna concepts to optics and quantum optics. Our research unravels how a resonant response to the magnetic field of light, combined with plasmonic resonances, gives rise to nanoscatterers and sources with surprising properties, in terms of directionality, polarization, and chirality.

  • Cord Müller

  • Invited speaker: Prof. Dr. Cord Müller
    Affiliation: National University of Singapore
    Title: Hot Times For Cold Atoms In Random Potentials
    Time and room: 17:15  lecture hall IAP

  • Axel Pelster

  • Invited speaker: Prof. Dr. Axel Pelster
    Affiliation: TU Kaiserslautern
    Title: Dipolar Bose-Einstein Condensates With Weak Disorder
    Time and room: 17:15  lecture hall IAP
    Abstract: The talk discusses several illustrative examples where ultracold dilute atomic gases provide important insights into condensed matter physics. We start with reviewing the properties of Bose-Einstein condensates (BECs) with the anisotropic and long-range dipole-dipole interaction. To this end we investigate the influence of quantum fluctuations upon the equilibrium configuration, the low-lying oscillation frequencies, and the time-of-flight dynamics. We find that both atomic magnetic and molecular electric dipolar BECs offer promising scenarios for detecting beyond mean-field effects. Furthermore, we report on recent progress in understanding the properties of ultracold bosonic atoms in potentials with quenched disorder. This notoriously difficult dirty boson problem is experimentally relevant for the miniaturization of BECs on chips and can also be studied by tailoring disorder potentials via laser speckle fields. Theoretically it is intriguing because of the competition of localization and interaction as well as of disorder and superfluidity.
    Finally, we combine both previous topics and consider the impact of weak disorder upon a
    polarized dipolar BEC at zero temperature. Surprisingly we find that disorder corrections of the
    superfluid density yield characteristic interaction-induced anisotropies which are not present in
    the absence of disorder.

  • Markus Lippitz

  • Invited speaker: Prof. Dr. Markus Lippitz
    Affiliation: Max-Planck-Institut für Festkörperforschung, Stuttgart
    Title: Nonlinear Spectroscopy Of A Single Nanoobject
    Time and room: 17:15  lecture hall IAP
    Abstract: Nanoobjects with a size between 1 and 100 nanometers show fascinating properties that deviate strongly from those of bulk solids. The plasmon resonance of metal nanoparticles or the electron confinement in quantum dots are prominent examples. However, even in the best preparation methods, nanoobjects differ from each other in size, shape, or local environment. Experiments on the single particle level allow the experimenter to circumvent the ensemble heterogeneity. In this presentation I will demonstrate nonlinear optical spectroscopy of a single nanoobject.

    Single nanoobjects, especially at room temperature, show only a weak interaction with light, as only a low number of electrons is involved. Nonlinear optical signals which are already weak for a bulk solid become difficult to detect. I will show how an optical nanoantenna is able to enhance the signal of a single nanoobject so that nonlinear spectroscopy becomes possible. We investigate the mechanical breathing mode of a single gold nanodisc by antenna-enhanced transient absorption spectroscopy [1].
    Very large optical nonlinearities can be found on optical two-level systems such as semiconductor quantum dots. Their quantum-optical properties find use as single photon source or quantum bit. However, to be really used, a quantum bit needs to be connected to some kind of circuit. I will give an overview of our work on coherent reading and writing of quantum bits [2] and their coupling to plasmonic nanocircuits [3].

    [1] T. Schumacher et al. , “Nanoantenna-enhanced ultrafast nonlinear spectroscopy of a single gold nanoparticle”, Nature Commun. 2 (2011) 333.

    [2] C. Wolpert et al., “Transient reflection: A versatile technique for ultrafast spectroscopy of a single quantum dot in complex environments”, Nano Letters 12 (2012) 453.

    [3] M. Pfeiffer et al. , “Enhancing the Optical Excitation Efficiency of a Single Self- Assembled Quantum Dot with a Plasmonic Nanoantenna”, Nano Letters 10 (2010) 4555.