Quantum technologies

2015

• F. König
  Exploration of Fiber Fabry-Perot Resonators as Optical Filters, (2015), Bachelor thesisBibTeX

2014

• R. Reimann
  Cooling and Cooperative Coupling of Single Atoms in an Optical Cavity, (2014), PhD thesisBibTeX
  ABSTRACT »

  In this work the motional state of single cesium atoms strongly coupled to an optical high-finesse cavity is controlled and manipulated by a novel Raman cooling scheme. Furthermore, cavity-modified super- and subradiant Rayleigh scattering of two atoms is observed and explained by collective coupling of the atoms to the cavity mode. We start with the description and comparison of different intra-cavity cooling schemes that allow us to control the motional states of atoms. Cavity cooling is experimentally and theoretically investigated for the two cases of pumping the cavity and driving the atom. In contrast to other cooling schemes, such as EIT- or Raman cooling, our analysis shows that we cannot use cavity cooling for efficient ground-state preparation, but it serves as a precooling scheme for the sideband-cooling methods. Comparing the more efficient sideband cooling techniques EIT and Raman cooling, we find that the experimental efficiency of EIT cooling could not be determined. Therefore we choose a novel, easily implemented Raman cooling technique that features an intrinsic suppression of the carrier transition. This is achieved by trapping the atom at the node of a blue detuned intra-cavity standing wave dipole trap that simultaneously acts as one field for the two-photon Raman coupling. We apply this method to perform carrier-free Raman cooling to the two-dimensional vibrational ground state and to coherently manipulate the atomic motion. The motional state of the atom after Raman cooling is extracted by Raman spectroscopy using a fast and non-destructive atomic state detection scheme, whereby high repetition rates and good signal-to-noise ratios of sideband spectra are achieved. In a last experiment we observe cooperative radiation of exactly two neutral atoms strongly coupled to our cavity. Driving both atoms with a common laser beam, we measure super- and subradiant Rayleigh scattering into the cavity mode depending on the relative distance between the two atoms. Surprisingly, due to cavity backaction onto the atoms, the cavity output power for superradiant scattering by two atoms is almost equal to the single atom case. We explain these effects quantitatively by a classical model as well as by a quantum mechanical one based on Dicke states. Furthermore, information on the relative phases of the light fields at the atom positions are extracted, and the carrier-free Raman cooling scheme is applied to reduce the jump rate between super- and subradiant configurations.

2011

• S. Brakhane
  Kontrolle der Atom-Resonator-Wechselwirkung mit Hilfe einer Regelschleife, (2011), Diplom thesisBibTeX

• T. Kampschulte
  Coherently driven three-level atoms in an optical cavity, (2011), PhD thesisBibTeX
  ABSTRACT »

  We experimentally realize strong light-matter coupling of a single cesium atom to a single mode of a high-finesse optical cavity. In this regime, the optical properties of one atom change the transmission spectrum of the resonator significantly. The two hyperfine ground states of cesium can be distinguished by the relative transmission of a weak probe beam coupled to the cavity. Here, we coherently couple the two hyperfine ground states via an electronically excited state with two-photon transitions. In the first experimental configuration, two-photon Raman transitions are driven between the two ground states while continuously observing the atomic state. I present a new in-situ spectroscopic technique for the internal hyperfine and Zeeman-sublevel dynamics of an atom inside the cavity mode, using time-dependent Bayesian analysis of quantum jumps. In the second configuration, the three-level atomic structure forms the basis of Electromagnetically Induced Transparency (EIT). The modification of the absorptive and dispersive properties of an atom by destructive interference leads to strong changes in the transmission of the probe beam. Our observations are qualitatively described in a semiclassical picture in the weak-probing limit. I furthermore present a fully quantum mechanical model, where deviations from the weak-probing limit, dephasing effects and other hyperfine states are taken into account to fit our data quantitatively. Moreover, I formulated an extension of the semiclassical model to highlight a conceptual contrast to the quantum model. Additionally, the EIT effect is connected with a strong cooling effect, resulting in a 20-fold increase of the storage time of the atoms inside the cavity. I present further results of investigations of this effect where the atoms are trapped and EIT-cooled outside the cavity. From microwave sideband spectra it can be inferred that almost 80% of the atoms are in the ground state of motion along the trap axis. ------ Copyright notice: Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modified, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.

2010

• M. Eckstein
  Three-Level Physics of a Single Atom Coupled to a High Finesse Cavity, (2010), Diplom thesisBibTeX

2009

• M. Khudaverdyan
  A controlled one and two atom-cavity system, (2009), PhD thesisBibTeX

• A. Thobe
  Quantum Jumps of One and Two Atoms in a Strongly Coupled Atom-Cavity System, (2009), Diplom thesisBibTeX

• S. Reick
  Internal and external dynamics of a strongly-coupled atom-cavity system, (2009), PhD thesisBibTeX

2008

• K. Schörner
  Ein phasenstabilisiertes Lasersystem für resonatorinduzierte Raman-Prozesse , (2008), Diplom thesisBibTeX

• K. Lenhard
  Stabilisierung eines Resonators hoher Finesse zur Atom-Lichtfeld-Kopplung, (2008), Diplom thesisBibTeX

2007

• I. Dotsenko
  Single atoms on demand for cavity QED experiments, (2007), PhD thesisBibTeX

• A. Stiebeiner
  Deterministische Kopplung eines einzelnen Atoms an die Mode eines Resonators hoher Finesse, (2007), Diplom thesisBibTeX

2006

• Y. Miroshnychenko
  An atom-sorting machine, (2006), PhD thesisBibTeX

2003

• W. Rosenfeld
  A high finesse optical resonator for cavity QED experiments, (2003), Diplom thesisBibTeX

2002

• Y. Miroshnychenko
  Design and test of an optical high finesse resonator for single atom experiments, (2002), Diplom thesisBibTeX