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Quantum technologies

Dieter Meschede's research group
Home AMO physics colloquia
Colloquia
  • Sven Höfling

    (13/06/16)
  • Invited speaker: Prof. Sven Höfling
    Affiliation: Universität Würzburg; University of St Andrews, UK

    Special Colloquium
    Title: Polariton Lasers

    Time and room:  16:15 h, lecture hall IAP

    More than a century after the introduction of incandescent lighting and half a century after the realization of semiconductor lasers, semiconductor light sources are continuing to revolutionize applications and having a paramount impact on our everyday life. The creativity of quantum and photonics engineers and material scientists results in semiconductor light emitting diodes and semiconductor lasers with unprecedented characteristics, including ever better efficiency or brightness and ultra-wide wavelength coverage. In this talk, after a summary of general semiconductor laser research undertaken in our group, I will focus on the description of a novel kind of coherent light emitter based on a semiconductor microcavity with embedded quantum wells. In contrast to conventional lasers, this sort of device, termed polariton laser, relies not on stimulated emission of photons but on stimulated scattering of bosonic quasiparticles, the polaritons. These devices have lower thresholds than conventional lasers, and I will describe the physics underlying these devices and routes towards possible practical applications.

  • Michael Johanning

    (07/06/16)
  • Invited speaker: Dr. Michael Johanning                             
    Affiliation: Universität Siegen
    Title: Scalable Quantum Information Processing in ion traps using MAGIC
    Time and room:  17:15 h, lecture hall IAP

    Ion traps are one of the promising platforms for quantum information processing and many proof of principle experiments have been realized with laser cooled trapped ions. A recent development is the application of inhomogeneous magnetic fields and microwave radiation for selective coherent manipulation and conditional dynamics. This allows for long coherence times and high fidelity one and two qubit gates, as demonstrated recently.

    In this talk, I will focus on the storage, manipulation and readout of qubits encoded in the spin degree of freedom which can interact, upon application of an additional magnetic field gradient, by a magnetic gradient induced coupling (MAGIC). I will illustrate the concepts using results obtained with macroscopic and micro-structured traps, and compare to atomic qubits manipulated by optical means.

  • Hans Peter Büchler

    (24/05/16)
  • Invited speaker: Prof. Hans Peter Büchler
    Affiliation: Universität Stuttgart
    Title: Strongly Interacting Rydberg Slow Light Polaritons

    Time and room:  17:15 h, lecture hall IAP

    Synthetic quantum materials offer an exciting opportunity to explore quantum many-body physics and novel states of matter under controlled conditions. In particular, they provide an avenue to exchange the short length scales and large energy scales of the solid state for an engineered system with better control over the system Hamiltonian, more accurate state preparation, and higher fidelity state readout. Here we propose a unique platform to study quantum phases of strongly interacting photons. We introduce ideas for controlling the dynamics of individual photons by manipulating the geometry of a multimode optical cavity, and combine them with recently established techniques to mediate strong interactions between photons using Rydberg atoms. We demonstrate that this approach gives rise to crystalline- and fractional quantum Hall- states of light, opening the door to studies of strongly correlated quantum many-body physics in a photonic material.

  • Wolfgang Schleich

    (03/05/16)
  • Invited speaker: Prof. Wolfgang Schleich
    Affiliation: Universität Ulm
    Title: The Riemann Zeta Function and Quantum Mechanics

    Time and room:  17:15 h, lecture hall IAP

    The Riemann zeta function ζplays a crucial role in number theory as well as physics. Indeed, the distribution of primes is intimately connected to the non-trivial zeros of this function. We briefly summarize the essential properties of the Riemann zeta function and then present a quantum mechanical system which when measured appropriately yields ζ. We emphasize that for the representation in terms of a Dirichlet series interference [1] suffices to obtain ζ. However, in order to create ζ along the critical line where the non-trivial zeros are located we need two entangled quantum systems [2]. In this way entanglement may be considered the quantum analogue of the analytical continuation of complex analysis.

    [1] R. Mack, J. P. Dahl, H. Moya-Cessa, W.T. Strunz, R. Walser and W. P. Schleich, Riemann ζ-function from wave packet dynamics, Phys. Rev. A. 82, 032119 (2010).

    [2] C. Feiler and W.P. Schleich, Entanglement and analytical continuation: an intimate relation told by the Riemann zeta function, New J. Phys. 15, 063009 (2013).

  • Christine Silberhorn

    (28/04/16)
  • Invited speaker: Prof. Christine Silberhorn
    Affiliation: Universität Paderborn
    Special Colloquium
    Title: Sum frequency generation for quantum applications

    Time and room: Thursday, April 28, 2016, Conference Room (311) IAP

    In recent years sum frequency conversion processes have become an established tool to implement quantum information transfer interfaces between systems of different wavelengths. Such interfaces are essential for the realization of quantum networks, which combine different individual components with incompatible frequencies. In particular, long distance quantum communication, which uses stationary qubits with transitions in the visible or UV and flying qubits at telecommunication wavelengths rely on practical quantum frequency converters. Here, we present our work on the realization of sum frequency generation processes from telecommunication regime to visible and UV wavelengths and discuss cw and pulsed light characteristics


Colloquia