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Quantentechnologie

Dieter Meschedes Forschungsgruppe
Home AMO-Physikkolloquien
Colloquia
  • Kubanek

    (21/05/19)
  • Invited speaker: Alexander Kubanek
    Affiliation: Universität Ulm
    Title: Spin-Photon Interface of SiV- Center in Nanometer-Sized Diamond Host

    Time and room: 17:15, lecture hall IAP
    Abstract: Implementing efficient, highly controllable light-matter interfaces is essential to realizing the goal of solid-state quantum networks. The negatively charged silicon-vacancy (SiV-) center in diamond is a promising candidate for such interfaces due to favorable optical properties and long coherence times at low temperatures. Creating optical links between remote SiV centers via photon-mediated spin-spin entanglement is an outstanding challenge. An efficient link could be realized by Purcell-enhanced optical transitions by means of optical resonators. The integration of the diamond host into the mode of an optical resonator is demanding and requires, e.g., absence of scattering and optimized coupling. Therefore small dimensions are favorable. However, the resulting proximity of the quantum emitter to the surface of the host matrix typically degrades the optical and coherence properties.
    In this talk I will present our work on how to obtain single SiV- centers per one nanodiamond with ideal optical properties. I will discuss the integration of SiV centers into photonic structures and analyze the achieved coupling efficiency. Furthermore,
    I will discuss the integration of diamond membranes into fiber-based optical resonators without changing the properties of the cavity. We used the coupled system to extract the absorption cross section of SiV- centers.
    References
    [1] U. Jantzen et. al., New Journal of Physics (2016)
    [2] S. Häußler et. al., New Journal of Physics (2017)
    [3] S. Häußler et. al., Phys. Rev. B 99, 165310 (2019)
    [4] L. J. Rogers, et al., Phys. Rev. Applied 11, 024073 (2019)

  • Corkum

    (30/04/19)
  • Invited speaker: Paul Corkum
    Affiliation: Joint Attosecond Science Laboratory
    University of Ottawa and National Research Council of Canada
    Title: Vector Beams, High Harmonic Generation and THz Solenoidal Magnetic Fields 

    In the visible and infrared it is possible to transform a Gaussian beam into vortex beams – beams with orbital angular momentum.Such vortexbeams are important for advanced microscopy and for quantum optics.  But is orbital angular momentum conserved during high-harmonic generation?  We show the conservation of orbital angular momentum and show how it leads to a method for coupling a controlled orbital angular momentum on any harmonic. Our results open a pathway for attosecond science with similarly structured light.
    Besides shaping the wave fronts, a Gaussian beam can also be transformed into beams with complex polarization states–so called vector beams. We use an 800 nm, 2 mJ pulse, 35 fs pulse and a Q-plate (illustrated in the inset) to produce a vector beam with each quadrant circularly polarized, with adjacent quadrants delayed in phase by p/2 and with different handedness for adjacent quadrants (encoded in red and blue in the figure).  As such a vector beam propagates, it transforms into a beam with linearly polarized segments as illustrated (bottom left) and measured (bottom, middle).   We transform this beam via high-harmonic generation to photon energy of 40 eV creating a new vector beam with linearly polarized segments and also with adjacent quadrants phase delayed by pn/2 where n is the harmonic order.  This beam likewise transforms as it propagates into a beam with circularly polarized segments as illustrated in the 3-dimensional figure.
    I conclude by discussing how, when vector beams are combined with coherent control, we can produce high-intensity, THz, solenoidal magnetic fields.
     

  • Elsässer

    (30/04/19)
  • Invited speaker: Thomas Elsässer
    Affiliation: Max Born-Institut, Berlin
    Title: Phonon-Driven Charge Dynamics in Solids – New Insight from Ultrafast Terahertz and X-Ray Experiments
    Time and room: 17:15, lecture hall IAP
    Abstract: The interplay of charge and lattice excitations has a decisive influence on the electronic and optical properties of polar and ionic crystals. Specific low-frequency phonons, the so-called soft modes, are strongly coupled to the electronic system and induce strong relocations of electronic charge in space and time. New methods of nonlinear terahertz spectroscopy and femtosecond x-ray diffraction allow for mapping such dynamics in a temporally and spatially resolved way. In this talk, recent results on phonon-driven charge dynamics in prototype molecular materials are presented. In polycrystalline aspirin (acetylsalicylic acid), rotations of methyl groups with a sub-picometer displacement induce charge relocations on the 100 pm length scale of chemical bonds [1,2]. In ferroelectric ammonium sulfate, the macroscopic electric polarization is periodically reversed by excitation of a soft-mode with a period of a few picoseconds [3]. A theoretical analysis of time dependent charge densities establishes a direct link between microscopic electron distributions and macroscopic electric properties [4].
    [1] G. Folpini et al., Phys. Rev. Lett. 119, 097404(2017)
    [2] C. Hauf et al., Struct. Dyn. 6,014503 (2019)
    [3] C. Hauf et al., Struct. Dyn. 5,024501 (2018)
    [4] C. Hauf, M. Woerner, C. Hauf, T. Elsaesser, Phys. Rev. B 98,054306 (2018)

    AUSGEWÄHLT
  • Schreiber

    (23/04/19)
  • Invited speaker: Jörg Schreiber
    Affiliation: LMU München
    Title: Laser-Driven Swift Ion Bunches

    Time and room: 17:15, lecture hall IAP
    Abstract: My group at the Chair for Medical Physics at the LMU Munich investigates the acceleration of ion bunches trough the interaction of laser pulses at relativistic intensities with plasmas. Over the last 15 years, Laser-ION (LION) acceleration has been the focus of intense research, which I will review in my talk. Our main objective is to realize viable sources for applications in radiation physics, material science, chemistry, biology and medicine. Currently, we establish the Centre for Advanced Laser Applications (CALA), which will feature a laser system able to provide 20 fs short laser pulses with peak power of up to 3 Peta-Watt.
    This talk will provide information on the ultrafast processes that lead to the acceleration of ions to kinetic energies from a few to 10s of MeV per nucleon. I will highlight challenges and limits of our current understanding and explain latest break-through demonstrations. The difficulty of advancing laser-driven ion acceleration into integrated laser-driven ion acceleration systems (ILDIAS) mainly originates from the fact that in the focus of a PW-laser pulse, the light intensities rise from the damage threshold of solid matter (~1013W/cm²) via relativistic intensities (1018W/cm²) to the maximum intensity (1020…1022W/cm²) within a few 10s of picoseconds. The actual acceleration phase in electric fields of the order MV/µm happens within a few 10s of femtoseconds. This extraordinary acceleration though enables unique characteristics of ion bunches to be exploited. I will explain three recent examples that range from sub-picosecond resolved ion induced dynamics in solids to the generation of soundwaves in water on the microsecond scale.

     

  • Bernhardt

    (16/04/19)
  • Invited speaker: Brigitta Bernhardt
    Affiliation: Universität Jena
    Title: Novel Applications for Dual Comb Spectroscopy

    Time and room: 17:15, lecture hall IAP
    Abstract:  Dual comb spectroscopy, an innovative form of traditional Fourier transform spectroscopy, combines broad spectral coverage and short measurement times with simultaneously unprecedented spectral resolution. Having its origin in gas phase measurements, we recently extended the application field of dual comb spectroscopy to liquid samples with additional µm spatial resolution via hyperspectral imaging and Raman spectroscopy.
    Due to the versatility of the method, a variety of dual comb spectrometers have been realized lately in the THz, visible and infrared spectral region but not yet in the (extreme) ultraviolet (XUV). Our recent efforts towards this development are discussed in the talk. This extension towards the XUV opens up also new potential applications aiming at solid state samples such as high resolution imaging of semiconductor chips.
     


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