IAP logo UniBonn logo
  • Increase font size
  • Default font size
  • Decrease font size

Quantum technologies

Dieter Meschede's research group
Theses - FCQED


  • M. M. Dorantes
    Fast non-destructive internal state detection of neutral atoms in optical potentials, (2016), PhD thesisBibTeXPDF

    Neutral atoms trapped in optical lattices are promising candidates for quantum information processing and quantum simulation. Over the last decades, elegant tools for the manipulation of the internal and external states of optically trapped atoms have been developed. The crucial capability of scalable internal state readout in these systems, however, still relies on destructive methods. In spite of the important role of near-resonant illumination for the manipulation and detection of atoms in the lattice, there also exists a significant lack of studies on the heating and cooling dynamics of optically trapped atoms interacting with near-resonant light. An in-depth understanding of the heating and cooling processes is essential to finding the conditions of illumination that enable the non-destructive internal state readout of multiple atoms.

    This work presents an experimental system to cool, trap, manipulate, and detect the internal and external states of a small ensemble of 87Rb neutral atoms trapped in a one-dimensional optical lattice. A high photon detection efficiency in our experimental system allows for fast fluorescence imaging with acquisition times of 20 ms and fast position determination of atoms in the optical lattice with an accuracy of ∼40 nm.

    Using this experimental system, we investigate the heating dynamics of a neutral atom trapped in a standing wave dipole trap illuminated by a single near-resonant laser beam. A theoretical description to describe our measurements is provided in two experimentally relevant regimes. First, we consider the case of a weak near-resonant beam and later the case of off-resonant illumination. From this analysis, we find settings for the illumination light which allows an atom to scatter many photons before it is expelled from the trap.

    Building on these results we demonstrate simultaneous, non-destructive determination of the internal state of spatially resolved atoms trapped in a one-dimensional optical lattice with a fidelity of 98.6 ± 0.2% and a survival probability of 99.0 ± 0.2%. During the readout process, less than 2% of the atoms change their initial ground state.

    In order to determine the state of atoms that are not spatially resolved, a novel image analysis technique is presented. The technique uses Bayesian methods, which include the statistics of the detected photons as well as the response from the EMCCD camera. The Bayesian method is implemented on experimental data for atoms trapped in a one-dimensional optical lattice and its accuracy is tested by numerical simulations. In addition, an extension of this algorithm for atoms trapped in two-dimensional lattices is provided.

    Finally, the non-destructive state detection method is utilized as a tool for the state determination following the coherent control of the internal and external states of atoms in the optical trap. Here Raman sideband cooling is implemented and utilized in an atomic compression sequence for the creation of a small and dense atomic ensemble. These techniques will play an important role in experiments studying the collective light interaction of the atomic ensemble in a recently added optical fiber cavity.


  • S. Urban
    Optimization of an optical fiber endfacet machine, (2013), Bachelor thesisBibTeX


  • F. Seidler
    Aufbau einer Maschine zur Bearbeitung von Glasfaser-Endflächen, (2012), Bachelor thesisBibTeX
    Der einfachste Optische Resonator besteht aus zwei einander gegenüber positionierten Spiegeln (ein sogenannter Fabry-Pérot-Resonator). Die Eigenschaften dieser Resonatoren hängen stark von Form, Oberfläche und Positionierung der verwendeten Spiegel ab. Um einen besonders vorteilhafte Satz an Parametern für Experimente auf dem Gebiet der CQED (Cavity Qantum Electro Dynamics) zu erhalten, möchte man die Endflächen von Glasfasern als Spiegel verwenden. Dies setzt insbesondere eine Möglichkeit zur Bearbeitung der Faserendflächen voraus.Grundlegende Zusammenhänge und Eigenschaften dieser Faser-Fabry-Pérot Resonatoren, wie auch theoretische Betrachtungen zur gewählten Bearbeitungsmethode für die Faserendflächen folgen in Kapitel 2. Anschließend wird der Aufbau einer Maschine zur Bearbeitung von Faserendflächen geschildert (Kapitel 3). Erste Tests werden in Kapitel 4 dargelegt. Abschließend wird ein Ausblick auf noch ausstehende Arbeiten gegeben, die schließlich die Herstellung von Faserresonatoren im gewünschten Rahmen ermöglichen sollen (Kapitel 5).