55 research outputs found
Coherent manipulation of Bose-Einstein condensates with radio-frequency adiabatic potentials on atom chips
During this thesis a novel trapping and manipulation technique for neutral atoms on atom chips has been developed and experimentally implemented. Radio-frequency (rf) coupling of internal states of magnetically trapped atoms results in versatile microscopic potentials, which overcome various limitations of static magnetic traps. An extensive experimental analysis of this new technique has been carried out, exploring the state-dependency of the rf potentials and the possible realization of non-trivial trapping geometries. Based on these results, the first coherent matter wave beam splitter on an atom chip has been realized, demonstrating for the first time the all-magnetic coherent splitting of a condensate. This new atom optical tool has then been applied to investigate the phase-properties of one-dimensional Bose-Einstein condensates. The potential configuration developed during this thesis provides direct access to the phase fluctuations in the system and has allowed the first time-resolved study of equilibrium properties and non-equilibrium dynamics in a one-dimensional Bose gas
Electromagnetically induced transparency of ultralong-range Rydberg molecules
We study the impact of Rydberg molecule formation on the storage and
retrieval of Rydberg polaritons in an ultracold atomic medium. We observe
coherent revivals appearing in the retrieval efficiency of stored photons that
originate from simultaneous excitation of Rydberg atoms and Rydberg molecules
in the system with subsequent interference between the possible storage paths.
We show that over a large range of principal quantum numbers the observed
results can be described by a two-state model including only the atomic Rydberg
state and the Rydberg dimer molecule state. At higher principal quantum numbers
the influence of polyatomic molecules becomes relevant and the dynamics of the
system undergoes a transition from coherent evolution of a few-state system to
an effective dephasing into a continuum of molecular states.Comment: Submitted to PR
Metastable decoherence-free subspaces and electromagnetically induced transparency in interacting many-body systems
We investigate the dynamics of a generic interacting many-body system under
conditions of electromagnetically induced transparency (EIT). This problem is
of current relevance due to its connection to non-linear optical media realized
by Rydberg atoms. In an interacting system the structure of the dynamics and
the approach to the stationary state becomes far more complex than in the case
of conventional EIT. In particular, we discuss the emergence of a metastable
decoherence free subspace, whose dimension for a single Rydberg excitation
grows linearly in the number of atoms. On approach to stationarity this leads
to a slow dynamics which renders the typical assumption of fast relaxation
invalid. We derive analytically the effective non-equilibrium dynamics in the
decoherence free subspace which features coherent and dissipative two-body
interactions. We discuss the use of this scenario for the preparation of
collective entangled dark states and the realization of general unitary
dynamics within the spin-wave subspace.Comment: 13 pages, 3 figure
Emergent universal dynamics for an atomic cloud coupled to an optical wave-guide
We study the dynamics of a single collective excitation in a cold ensemble of
atoms coupled to a one-dimensional waveguide. The coupling between the atoms
and the photonic modes provides a coherent and a dissipative dynamics for this
collective excitation. While the dissipative part accounts for the collectively
enhanced and directed emission of photons, we find a remarkable universal
dynamics for increasing atom numbers exhibiting several revivals under the
coherent part. While this phenomenon provides a limit on the intrinsic
dephasing for such a collective excitation, a setup is presented, where this
remarkable universal dynamics can be explored.Comment: Main text: 5 pages, 3 figures, Supplement Material: 10 pages, 1
figur
- …