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Quantum technologies

Dieter Meschede's research group
Home AMO physics colloquia
  • Helmut Ritsch

  • Invited speaker: Prof. Helmut Ritsch
    Affiliation: Universität Innsbruck
    Title: Quantum Optics with Ultracold Quantum Gases: Towards the Full Quantum Regime of the Light-matter Interaction
    Time and room: 17:15 lecture hall IAP
    Abstract: As matter influences the propagation of light waves, light can be used to manipulate matter wave dynamics. In typical experiments as optical traps or cavity QED one of the two effects dominates. However, confining a cold atoms in a high finesse optical resonator creates a novel situation, where particles and photons are dynamically coupled by momentum and energy exchange on equal footing. The particles act as a dynamic refractive index for the light waves which can form structured optical potentials guiding the particles motion.
    The zero temperature limit of an atomic BEC in an optical lattice trapped in a high Q cavity represents a genuine quantum model system for quantum optics with quantum gases. Due to the dynamical entanglement of atomic motion and light in a weakly coupled system, a measurement of the scattered light detects atomic quantum statistics properties and projects the many-body atomic state to corresponding eigenstates. Similarly measurements on the atoms exhibit nonclassical properties of the light.
    For larger interaction strength the light induced long range coupling of the particles can induce regular crystallization of the particles bound by light and the appearance of new exotic quantum phases with short and long range order as found in a supersolid.
    H. Ritsch, P. Domokos, F. Brenneke and T. Esslinger, REV. MOD. PHYS. 85, 2013


  • Wolfram Pernice

  • Invited speaker: Dr. Wolfram Pernice,
    Affiliation: Karlsruhe Institute of Technology
    Title: Nanophotonics Meets Nanomechanics: Light Force Devices on a Chip
    Time and room: 17:15 lecture hall IAP
    Abstract: Radiation pressure forces exerted by photons are generally considered to be too weak for real-world applications. The picture changes, however, when moving to nano-scale dimensions, at which considerable momentum transfer can result from illumination with light. Here I will describe a chip-scale framework in which optical forces can be exploited as an efficient driving and sensing mechanism for nano-scale resonators. Besides allowing for unprecedented measurement sensitivity, such opto-mechanical interactions provide a new paradigm for coupling nano-mechanical and nano-photonic components. I will provide an overview over progress on integrated opto-mechanics and also present recent results for chip-scale optical computing and mechanical data storage.

  • Thilo Stöferle

  • Invited speaker: Dr. Thilo Stöferle,
    Affiliation: IBM Research GmbH, Zürich
    Title: Exciton-polariton Bose-Einstein Condensation With A Polymer At Room Temperature
    Time and room: 17:15 lecture hall IAP
    Abstract: We create exciton-polariton quasiparticles by exciting optically a microcavity filled with a ladder-type conjugated polymer in the strong coupling regime. At room temperature thermalization of these quasi-particles occurs while it is suppressed at low temperature because of a relaxation bottleneck. Above a certain excitation threshold with incoherent off-resonant picosecond laser pulses, we observe the emergence of non-equilibrium Bose-Einstein condensation in the lower polariton branch. This is evidenced by several distinct features such as a blue-shifted emission peak at zero in-plane momentum, accompanied by a nonlinear increase in the emission intensity and a sudden drop of the linewidth. Furthermore, the emission becomes polarized and the emission dynamics is drastically shortened. Spatially-resolved measurements with a Michelson interferometer show a macroscopic phase relation over almost the whole spot, and the fringe pattern exhibits non-flat phase fronts and fork-like dislocations, indicating a large number of vortices and excitations. In contrast to conventional lasing, we find a strong increase in threshold when decreasing the temperature, which can be explained by the peculiar thermalization properties. As we are able to obtain single-shot measurements of the spectrum and the interference patterns, we can study single realizations of the condensate.


  • Subhasis Sinha

  • Invited speaker: Prof. Subhasis Sinha
    Affiliation: IISER Kolkata
    Title: Sonderkolloquium:

               Correlated Phases And Excitations Of Rydberg Atoms In An Optical Lattice
    Time and room: 14:15 lecture hall IAP


  • Józef Fortágh

  • Invited speaker: Prof. Józef Fortágh
    Affiliation: Universität Tübingen
    Title: Interfacing Cold Atoms And Nanostructures
    Time and room: 17:15 lecture hall IAP