78 research outputs found
Dynamics and phase evolution of Bose-Einstein condensates in one-dimensional optical lattices
We report experimental results on the dynamics and phase evolution of
Bose-Einstein condensates in 1D optical lattices. The dynamical behaviour is
studied by adiabatically loading the condensate into the lattice and
subsequently switching off the magnetic trap. In this case, the condensate is
free to expand inside the periodic structure of the optical lattice. The phase
evolution of the condensate, on the other hand, can be studied by
non-adiabatically switching on the periodic potential. We observe decays and
revivals of the interference pattern after a time-of-flight.Comment: 6 pages, 5 figures; submitted to the Proceedings of the 11th Laser
Physics Workshop, Bratislava 200
Rydberg excitation of a Bose-Einstein condensate
We have performed two-photon excitation via the 6P3/2 state to n=50-80 S or D
Rydberg state in Bose-Einstein condensates of rubidium atoms. The Rydberg
excitation was performed in a quartz cell, where electric fields generated by
plates external to the cell created electric charges on the cell walls.
Avoiding accumulation of the charges and realizing good control over the
applied electric field was obtained when the fields were applied only for a
short time, typically a few microseconds. Rydberg excitations of the
Bose-Einstein condensates loaded into quasi one-dimensional traps and in
optical lattices have been investigated. The results for condensates expanded
to different sizes in the one-dimensional trap agree well with the intuitive
picture of a chain of Rydberg excitations controlled by the dipole-dipole
interaction. The optical lattice applied along the one-dimensional geometry
produces localized, collective Rydberg excitations controlled by the
nearest-neighbour blockade.Comment: 7 pages, 7 figures, Laser Physics in press. arXiv admin note: text
overlap with arXiv:1103.423
Stimulated Emission Tomography: Beyond Polarization
In this work we demonstrate the use of stimulated emission tomography to
characterize a hyper-entangled state generated by spontaneous parametric
down-conversion in a CW-pumped source. In particular, we consider the
generation of hyper-entangled states consisting of photon pairs entangled in
polarisation and path. These results extend the capability of stimulated
emission tomography beyond the polarisation degree of freedom, and demonstrate
the use of this technique to study states in higher dimension Hilbert spaces
Excitation and damping of collective modes of a Bose-Einstein condensate in a one-dimensional lattice
The mode structure of a Bose-Einstein condensate non-adiabatically loaded
into a one-dimensional optical lattice is studied by analyzing the visibility
of the interference pattern as well as the radial profile of the condensate
after a time-of-flight. A simple model is proposed that predicts the short-time
decrease of the visibility as a function of the condensate parameters. In the
radial direction, heavily damped oscillations are observed, as well as an
increase in the condensate temperature. These findings are interpreted as a
re-thermalization due to dissipation of the initial condensate excitations into
high-lying modes.Comment: 5 pages; submitted to PR
Sympathetic cooling and collisional properties of a Rb-Cs mixture
We report on measurements of the collisional properties of a mixture of
Cs and Rb atoms in a magnetic trap at
temperatures. By selectively evaporating the Rb atoms using a radio-frequency
field, we achieved sympathetic cooling of Cs down to a few . The
inter-species collisional cross-section was determined through rethermalization
measurements, leading to an estimate of for the s-wave scattering
length for Rb in the and Cs in the magnetic
states. We briefly speculate on the prospects for reaching Bose-Einstein
condensation of Cs inside a magnetic trap through sympathetic cooling
Hitting a BEC with a comb: Evolution of interference patterns inside a magnetic trap
We study the evolution inside a harmonic trap of Bose-Einstein condensates
released from the periodic potential of an optical lattice. After a
time-of-flight, harmonic motion of the interference peaks is observed as well
as a breathing motion in the direction perpendicular to the optical lattice. We
interpret these results in terms of a simple physical model and discuss the
possibility of more detailed studies of such a system.Comment: 10 pages, 3 figures; submitted to the Journal of Optics B special
issue on the "7th International Conference on Atom Optics and Interferometry"
(Lunteren, 2002
Rubidium Rydberg macrodimers
We explore long-range interactions between two atoms excited into high
principal quantum number n Rydberg states, and present calculated potential
energy surfaces (PES) for various symmetries of doubly excited ns and np
rubidium atoms. We show that the PES for these symmetries exhibit deep (~GHz)
potential wells, which can support very extended (~micrometers) bound
vibrational states (macrodimers). We present n-scaling relations for both the
depth De of the wells and the equilibrium separations Re of these macrodimers,
and explore their response to small electric fields and stability with respect
to predissociation. Finally, we present a scheme to form and study these
macrodimers via photoassociation, and show how one can probe the various
\ell-character of the potential wells
Ion detection in the photoionization of a Rb Bose-Einstein condensate
Two-photon ionization of Rubidium atoms in a magneto-optical trap and a
Bose-Einstein condensate (BEC) is experimentally investigated. Using 100 ns
laser pulses, we detect single ions photoionized from the condenstate with a
35(10)% efficiency. The measurements are performed using a quartz cell with
external electrodes, allowing large optical access for BECs and optical
lattices.Comment: 14 pages, 7 figure
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