University thesis:
Dissertation, Albert-Ludwigs-Universität Freiburg, 2017
Footnote:
cc_by_nc_nd http://creativecommons.org/licenses/by-nc-nd/4.0/deed.de cc
Description:
Abstract: Isolating ions and atoms from the environment is essential in experiments on a quantum level. For decades, this has been achieved by trapping ions with radiofrequency (rf) fields and neutral particles with optical fields. Trapping of ions by interaction with light without any rf fields has been demonstrated in 2010. These results can be seen as a starting point for finally combining the advantages of optical trapping and ions. In particular, ions provide individual addressability, high fidelities of operations and long-range Coulomb interaction, significantly larger compared to those of neutral atoms and molecules. The advantages of optical ion trapping are evident for example in the field of ultracold chemistry. By trapping ions optically the inevitable excess kinetic energy in hybrid traps, where ions are kept but also driven by rf-fields, is circumvented. Thus, optically trapped ions, which are embedded into and sympathetically cooled by quantum degenerate (neutral) gases, are expected to reach temperatures 4-5 orders of magnitude below the current state-of-the-art. This finally permits to enter the temperature regime where quantum effects are predicted to do-minate. In the first optical ion trapping experiments, the performance was dominated by the large off-resonant absorption rate of photons. This limited the temperature and lifetime of the optically trapped ions to millikelvin and milliseconds, respectively, and rendered the method not applicable to investigate the quantum behavior of ions, or ions and atoms. In this thesis the performance of optical ion trapping is enhanced significantly to allow for investigation of the trapping method with regard to performing ultracold atom-ion experiments. A new apparatus is presented, capable of simultaneously trap-ping Barium (138 Ba+) ions and Rubidium (87Rb) atoms with optical fields. Heating and photon-scattering rates are measured and revealed to be sufficiently low to allow for sympathetic cooling of the ion with an atomic cloud. Furthermore, the now achieved high isolation of an optically trapped ion is witnessed by a lifetime of an ion in an optical potential exceeding the former state-of-the-art by three orders of magnitude. This allows for sympathetic cooling to be efficient even at reduced atom densities and mitigates competing loss mechanisms such as interatomic neutral three-body collisi-ons. In addition, first experiments combining atoms and ions are presented, showing a clear signal of ...