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Quantum technologies

Dieter Meschede's research group
Home AMO physics colloquia
Colloquia
  • Prof. Axel Kuhn

    (05/09/11)
  • Invited speaker: Prof. Axel Kuhn
    Affiliation: University of Oxford
    Title: Single-Photon Shaping and Storage in Cavity-QED (or the "Tower-Bridge Photon")
    Time and room: 17:15, seminar room 1 in HISKP
    Abstract: We investigate the feasibility of implementing elementary light-matter interfaces for quantum networking. The combination of a deterministic single photon source based on vacuum stimulated adiabatic rapid passage [1,2], and a quantum memory is outlined [3,4]. Both systems are able to produce and process temporally shaped photonic wavepackets, and also provide a way of maintaining the indistinguishability of retrieved and original photons.

    Single atoms coupled to high-finesse cavities provide a unique way to deterministically generate a stream of single photons of small bandwidth [1]. We report on our latest results obtained with a strongly coupled atom-cavity system based on 87Rb. Atoms are injected into the cavity (Finesse F=80,000, L=80 μm) with an atomic fountain, which gives rise to atom-cavity interaction times of up to 0.5 ms. We demonstrate that this arrangement is a highly efficient source delivering indistinguishable single photons of arbitrary temporal shape [5], and we show how to derive analytic expressions for the optimum driving laser pulse [2]. Furthermore, we show that one can successfully imprint arbitrary phase jumps to individual photons and monitor these with a two-photon interference experiment of the Hong-Ou-Mandel type. Based on the successful photon generation, it is discussed how to invert the process such that a single atom absorbs a single impinging photon of arbitrary given shape with a probability close to unity. To do so, we analytically derive the shape of the driving pulse required to maintain impedance matching of the cavity to the incoming photonic wavepacket throughout its whole duration [4].

    We also report on the control of trapped atoms with optical tweezers [6]. This new technique allows handling many atoms independently, and therefore paves the way to QIP with scalable atomic arrays.

    [1] A. Kuhn and D. Ljunggren, “Cavity-based single-photon sources,” Contemporary Physics 51, 289 (2010); [2] G.S. Vasilev, D. Ljunggren, and A. Kuhn, “Single-photons made-to-measure,” New Journal of Physics 12, 063024 (2010); [3] M. Himsworth, P.B.R. Nisbet, J. Dilley, G. Langfahl-Klabes, and A. Kuhn, “EIT-based quantum memory for single photons from cavity-QED,” Appl. Phys. B 103, 579-589 (2011); [4] J. Dilley, P.B.R. Nisbet, B.W. Shore, and A. Kuhn, “Cavity-based single-atom quantum memory,” submitted, arXiv:1105:1699 [quant-ph]; [5] P. Nisbet, J. Dilley, and A. Kuhn, “Highly efficient source for indistinguishable photons of controlled shape,” submitted, arXiv:1106.6292v1 [quant-ph]; [6] L. Brandt, C. Muldoon, T. Thiele, J. Dong, E. Brainis, and A. Kuhn, “Spatial light modulators for the manipulation of individual atoms,” Appl. Phys. B 102, 443-450 (2011)

  • Prof. Mark Saffman

    (05/09/11)
  • Invited speaker: Prof. Mark Saffman
    Affiliation: University of Wisconsin
    Title: Towards a 2D array of quantum gates with Rydberg atom interactions
    Time and room: 15:45, seminar room 1 in HISKP
    Abstract: I will review recent experiments on Rydberg state mediated entangling quantum gates. The long range nature of the Rydberg interaction appears promising for scaling to an array of fully interconnected quantum bits. I will discuss approaches based on single atom, as well as ensemble qubits, and present progress towards multi-qubit experiments.

  • Prof. Jakob Reichel

    (05/09/11)
  • Invited speaker: Prof. Jakob Reichel
    Affiliation: ENS, Paris
    Title: Collective cavity QED with atomic Bose-Einstein condensates and exciton-polaritons
    Time and room: 15:00, seminar room 1 in HISKP

  • T. Kampschulte's defense

    (05/09/11)
  • PhD defense: Tobias Kampschulte
    TitleCoherently driven three-level atoms in an optical cavity
    Time and room: 10:00, seminar room 1 in HISKP
  • Prof. Matthias Weidemüller

    (12/07/11)
  • Invited speaker: Prof. Matthias Weidemüller
    Affiliation: Ruprecht-Karls-Universität Heidelberg
    Title: Rydberg Aggregates
    Time and room: 17 h c.t., lecture hall IAP
    Abstract: Due to the long-range character of the interaction between highly excited atoms, the dynamics of an ultracold gas of Rydberg atoms is entirely determined by van-der-Waals and dipole-dipole interactions. One outstanding property is the tunability of the strength and the character of the interactions with static electric fields. This allows one to explore the transition from a weakly coupled two-body system to a strongly coupled many-body system. The long-range interaction leads to many-body entanglement and has possible applications in quantum computing. In my talk I will first give a general introduction into the field of Rydberg gases with special emphasis on our recent experiments.