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Quantum technologies

Dieter Meschede's research group
Home AMO physics colloquia
  • Dr. Peter Rosenbusch

  • Invited speaker: Dr. Peter Rosenbusch
    Affiliation: Observatoire de Paris
    Title: Atomic Clocks, Exchange Interaction And Giant Coherence Times
    Time and room: 17:15, lecture hall IAP
    Abstract: Thanks to atomic clocks the second is the best realised SI unit with a relative accuracy of today 2x 10^-16. In addition to time keeping, these laboratory devices perform powerful tests of fundamental physics such as tests of general relativity or the constancy of constants. The SYRTE is the French national laboratory of standards regarding time and frequency. It operates about 15 clocks and interferometers using laser cooled atoms of various kinds. We will present an overview of the SYRTE’s activities including strategies to improve the clock and interferometer sensitivity. We will focus on a Trapped Atom Clock on a Chip, where magnetic confinement is used to increase the experiment time and hence reduce the spectroscopic linewidth. The trap increases the atom density by 4 orders of magnitude such that novel phenomena arise from the atom-atom interactions: for an ensemble of thermal atoms, we observe giant coherence times of 58+/-12 s. The underlying new mechanism based on the exchange interaction is of such a general nature that it is applicable in many cold atom experiments and possibly other systems.

  • Serge Rosenblum

  • Invited speaker: Serge Rosenblum
    Affiliation: Faculty of Chemistry, Weizmann Institute of Science, Rehovot, Israel
    Time and room: 9:00 h, IAP Conference Room

  • Prof. Axel Kuhn

  • 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

  • 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

  • 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