Quantum manipulation of (ultra-)cold atom systems for information processing

Abstract This work is split into two parts, in part one of this thesis we report on the improvement of the lifetime of a quantum memory based on neutral atoms while in part two we will focus on a new setup to perform experiments on neutral atoms within a 2D optical lattice. In the quantum memory experiment we used a blue-detuned optical dipole trap to confine the atoms in a minimum intensity region of the light beam, reducing dephasing due to differential light shift. We saw improvement in comparison to a previous experiment using red-detuned dipole traps. The anticipated lifetime could not be reached, however. We observed oscillations of the retrievability of our stored state which we explain by the evolution of the transversal component of the spinwave using Monte-Carlo simulations. In the second part we report on our new setup, built to investigate a broad range of experiments regarding 2D physics on optical lattices. This field is of special interest as it allows to simulate Hamiltonians of a wide range e.g. from solid state physics and opens possibilities regarding large-scale Entanglement/one-way computing. In particular we discuss 2D Mott-insulators, 2D-Bloch oscillation induced transport phenomena and ring-exchange in a superlattice plaquette

Transverse Mode Revival of a Light-Compensated Quantum Memory

A long-lived quantum memory was developed based on light-compensated cold $^{87}$Rb atoms in a dipole trap. The lifetime of the quantum memory was improved by 40 folds, from 0.67 ms to 28 ms with the help of a compensation laser beam. Oscillations of the memory efficiency due to the transverse mode breathing of the singly-excited spin wave have been clearly observed and clarified with a Monte-Carlo simulation procedure. With detailed analysis of the decoherence processes of the spin wave in cold atomic ensembles, this experiment provides a benchmark for the further development of high-quality quantum memories.Comment: 4 pages, 4 figure

Improving system of objectives maturity through systematic reuse of knowledge using ontology-based knowledge representations

Technical products are developed to meet the needs of different stakeholders. In addition, various constraints from all phases of the product life cycle have to be considered. In existing work, this information and its dependencies are systematically represented in the so-called system of objectives. A major challenge in modeling the system of objectives is that the necessary information in the system of objectives is often incomplete and uncertain. In addition, this uncertainty and the maturity of the system of objectives cannot be directly quantified because the target state of the system of objectives often cannot be unambiguously described. This research investigates a methodical approach to assess and improve the maturity of the system of objectives. Two means to reduce uncertainty and thus increase the maturity of the system of objectives are the systematic reuse of knowledge and the systematic building of knowledge through verification and validation activities