165 research outputs found
Electric-field induced dipole blockade with Rydberg atoms
High resolution laser Stark excitation of np (60 < n < 85) Rydberg states of
ultra-cold cesium atoms shows an efficient blockade of the excitation
attributed to long-range dipole-dipole interaction. The dipole blockade effect
is observed as a quenching of the Rydberg excitation depending on the value of
the dipole moment induced by the external electric field. Effects of eventual
ions which could match the dipole blockade effect are discussed in detail but
are ruled out for our experimental conditions. Analytic and Monte-Carlo
simulations of the excitation of an ensemble of interacting Rydberg atoms agree
with the experiments indicates a major role of the nearest neighboring Rydberg
atom.Comment: 4 page
Efficient formation of deeply bound ultracold molecules probed by broadband detection
Using a non-selective broadband detection scheme we discovered an efficient
mechanism of formation of ultracold Cs molecules in deeply bound levels
() of their electronic ground state X. They are formed by
a one-photon photoassociation of ultracold cesium atoms in a manifold of
excited electronic states, followed by a two-step spontaneous emission cascade.
We were able to form about molecules per second in these low
vibrational levels of the ground state. This detection scheme could be
generalized to other molecular species for the systematic investigation of cold
molecule formation mechanisms.Comment: 4 page
Dipole blockade through Rydberg Forster resonance energy transfer
High resolution laser excitation of np Rydberg states of cesium atoms shows a
dipole blockade at F\"{o}rster resonances corresponding to the resonant
dipole-dipole energy transfer of the np + np → ns + (n + 1)s reaction.
The dipole-dipole interaction can be tuned on and off by the Stark effect, and
such a process observed for relatively low n (25 − 41) is promising for
quantum gate devices. Both Penning ionization and saturation in the laser
excitation can limit the range of observation of the dipole blockadeComment: number of pages:
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
Photoionization spectroscopy of excited states of cold cesium dimers
Photoionization spectroscopy of cold cesium dimers obtained by
photoassociation of cold atoms in a magneto-optical trap is reported here. In
particular, we report on the observation and on the spectroscopic analysis of
all the excited states that have actually been used for efficient detection of
cold molecules stabilized in the triplet a^3Sigma_u^+ ground state. They are:
the (1)^3Sigma_g^+ state connected to the 6s+6p asymptote, the (2)^3Sigma_g^+
and (2)^3Pi_g states connected to the 6s+5d asymptote and finally the
(3)^3Sigma_g^+ state connected to the 6s + 7s asymptote. The detection through
these states spans a wide range of laser energies, from 8000 to 16500 cm-1,
obtained with different laser dyes and techniques. Information on the initial
distribution of cold molecules among the different vibrational levels of the
a^3Sigma_u^+ ground state is also provided. This spectroscopic knowledge is
important when conceiving schemes for quantum manipulation, population transfer
and optical detection of cold cesium molecules.Comment: 24 pages, 11 figures. Note: tables are available separately. Accepted
in Molecular Physic
Entanglement of two individual atoms using the Rydberg blockade
We report on our recent progress on the manipulation of single rubidium atoms
trapped in optical tweezers and the generation of entanglement between two
atoms, each individually trapped in neighboring tweezers. To create an
entangled state of two atoms in their ground states, we make use of the Rydberg
blockade mechanism. The degree of entanglement is measured using global
rotations of the internal states of both atoms. Such internal state rotations
on a single atom are demonstrated with a high fidelity.Comment: Proceeding of the 19th International Conference on Laser Spectroscopy
ICOLS 2009, 7-13 June 2009, Hokkaido, Japa
Rydberg state mediated quantum gates and entanglement of pairs of neutral atoms
Experiments performed within the last year have demonstrated Rydberg state
mediated quantum gates and deterministic entanglement between pairs of trapped
neutral atoms. These experiments validate ten year old proposals for Rydberg
mediated quantum logic, but are only the beginning of ongoing efforts to
improve the fidelity of the results obtained and scale the experiments to
larger numbers of qubits. We present here a summary of the results to date,
along with a critical evaluation of the prospects for higher fidelity Rydberg
gates.Comment: submitted to ICAP 2010 proceeding
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
Dark state experiments with ultracold, deeply-bound triplet molecules
We examine dark quantum superposition states of weakly bound Rb2 Feshbach
molecules and tightly bound triplet Rb2 molecules in the rovibrational ground
state, created by subjecting a pure sample of Feshbach molecules in an optical
lattice to a bichromatic Raman laser field. We analyze both experimentally and
theoretically the creation and dynamics of these dark states. Coherent
wavepacket oscillations of deeply bound molecules in lattice sites, as observed
in one of our previous experiments, are suppressed due to laser-induced phase
locking of molecular levels. This can be understood as the appearance of a
novel multilevel dark state. In addition, the experimental methods developed
help to determine important properties of our coupled atom / laser system.Comment: 20 pages, 9 figure
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