13 research outputs found
Comparison of GPR results with UAV photogrammetry at a Roman villa rustica in Noricum (southern Bavaria)
Ground penetrating radar was used for mapping the layout of a Roman villa rustica. Adjacent rescue excavation results were mapped by UAV photogrammetry. The combination with a photogrammetric model enables a ground truthing of GPR result
Reconstructing a Romanesque church based on GPR results
We present an integrated prospection of the remains a medieval monastery in Lower Franconia (Germany) built over with a Renaissance castle. The geophysical data is combined with a photogrammetric model of the Renaissance castle. Based on the geophysical data, a virtual reconstruction of the medieval church was achieved
Interference pattern and visibility of a Mott insulator
We analyze theoretically the experiment reported in [F. Gerbier et al,
cond-mat/0503452], where the interference pattern produced by an expanding
atomic cloud in the Mott insulator regime was observed. This interference
pattern, indicative of short-range coherence in the system, could be traced
back to the presence of a small amount of particle/hole pairs in the insulating
phase for finite lattice depths. In this paper, we analyze the influence of
these pairs on the interference pattern using a random phase approximation, and
derive the corresponding visibility. We also account for the inhomogeneity
inherent to atom traps in a local density approximation. The calculations
reproduce the experimental observations, except for very large lattice depths.
The deviation from the measurement in this range is attributed to the
increasing importance of non-adiabatic effects.Comment: 6 pages, 4 figure
Phase coherence of an atomic Mott insulator
We investigate the phase coherence properties of ultracold Bose gases in
optical lattices, with special emphasis on the Mott insulating phase. We show
that phase coherence on short length scales persists even deep in the
insulating phase, preserving a finite visibility of the interference pattern
observed after free expansion. This behavior can be attributed to a coherent
admixture of particle/hole pairs to the perfect Mott state for small but finite
tunneling. In addition, small but reproducible ``kinks'' are seen in the
visibility, in a broad range of atom numbers. We interpret them as signatures
for density redistribution in the shell structure of the trapped Mott
insulator
Coherent collisional spin dynamics in optical lattices
We report on the observation of coherent, purely collisionally driven spin
dynamics of neutral atoms in an optical lattice. For high lattice depths, atom
pairs confined to the same lattice site show weakly damped Rabi-type
oscillations between two-particle Zeeman states of equal magnetization, induced
by spin changing collisions. This paves the way towards the efficient creation
of robust entangled atom pairs in an optical lattice. Moreover, measurement of
the oscillation frequency allows for precise determination of the spin-changing
collisional coupling strengths, which are directly related to fundamental
scattering lengths describing interatomic collisions at ultracold temperatures.Comment: revised version; 4 pages, 5 figure
Precision measurement of spin-dependent interaction strengths for spin-1 and spin-2 87Rb atoms
We report on precision measurements of spin-dependent interaction-strengths
in the 87Rb spin-1 and spin-2 hyperfine ground states. Our method is based on
the recent observation of coherence in the collisionally driven spin-dynamics
of ultracold atom pairs trapped in optical lattices. Analysis of the Rabi-type
oscillations between two spin states of an atom pair allows a direct
determination of the coupling parameters in the interaction hamiltonian. We
deduce differences in scattering lengths from our data that can directly be
compared to theoretical predictions in order to test interatomic potentials.
Our measurements agree with the predictions within 20%. The knowledge of these
coupling parameters allows one to determine the nature of the magnetic ground
state. Our data imply a ferromagnetic ground state for 87Rb in the f=1
manifold, in agreement with earlier experiments performed without the optical
lattice. For 87Rb in the f=2 manifold the data points towards an
antiferromagnetic ground state, however our error bars do not exclude a
possible cyclic phase.Comment: 11 pages, 5 figure