Potsdam University Potsdam Quantum Optics Group

Universität Potsdam
Institut für Physik
Karl-Liebknecht-Str. 24/25
14476 Potsdam-Golm
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 Research Topics
 Quantum degenerate gases
 

Summary

    Laser cooling techniques have realized the "coldest places in the Universe" where atoms and molecules move at speeds of few cm/s and temperatures below 1 nK. These dilute gases reach a quantum regime where their de Broglie wavelength is of the order of 1 micron and exceeds the interparticle distance. Bosonic particles form a macroscopic matter wave, fermionic atoms experience the pressure from Pauli repulsion, and quantum chemistry forms ultracold molecules.

Projects

    A cloud of ultracold Bosons in a trap provides a mechanical oscillator with weak damping. This has been used to measure small forces arising from the van der Waals-Casimir-Polder interaction between atoms and a macroscopic surface. We have formulated a quantum field theory of these long-range electromagnetic interactions that provides a microscopic picture where many-body corrections and the impact of the trap confinement can be studied.
  • Ph.D. thesis of J. Schiefele: "Casimir-Polder interaction in second quantization"
    In experiments, an ultracold (condensed) phase often coexists with thermally excited particles. In particular in low-dimensional systems, thermal fluctuations are significant and can broaden the Bose-Einstein phase transition into a cross-over. We are exploring the limits of mean-field techniques to handle this situation and compare numerical simulation schemes.

Participants and cooperations

Papers

Financial support

  • Deutsche Forschungsgemeinschaft DFG (German Research Council)
    Schwerpunktprogramm 1116 (Priority programme) "Interaction in ultra-cold atomic and molecular gases''
  • European Science Foundation ESF
    "Casimir" research network
    "BEC2000+" programme


   
   
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