72 research outputs found
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
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
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
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
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
Coherence as ultrashort pulse train generator
Intense, well-controlled regular light pulse trains start to play a crucial
role in many fields of physics. We theoretically demonstrate a very simple and
robust technique for generating such periodic ultrashort pulses from a
continuous probe wave which propagates in a dispersive thermal gas media
Low-Energy Ions from Laser-Cooled Atoms
We report the features of an ion source based on two-color photoionization of a laser-cooled cesium beam outsourced from a pyramidal magneto-optical trap. The ion source operates in continuous or pulsed mode. At acceleration voltages below 300 V, it delivers some ten ions per bunch with a relative energy spread ÎUrms/Uâ0.032, as measured through the retarding field-energy-analyzer approach. Space-charge effects are negligible thanks to the low ion density attained in the interaction volume. The performances of the ion beam in a configuration using focused laser beams are extrapolated on the basis of the experimental results. Calculations demonstrate that our low-energy and low-current ion beam can be attractive for the development of emerging technologies requiring the delivery of a small amount of charge, down to the single-ion level and its eventual focusing in the 10-nm range
Optimal trapping wavelengths of Cs molecules in an optical lattice
The present paper aims at finding optimal parameters for trapping of Cs
molecules in optical lattices, with the perspective of creating a quantum
degenerate gas of ground-state molecules. We have calculated dynamic
polarizabilities of Cs molecules subject to an oscillating electric field,
using accurate potential curves and electronic transition dipole moments. We
show that for some particular wavelengths of the optical lattice, called "magic
wavelengths", the polarizability of the ground-state molecules is equal to the
one of a Feshbach molecule. As the creation of the sample of ground-state
molecules relies on an adiabatic population transfer from weakly-bound
molecules created on a Feshbach resonance, such a coincidence ensures that both
the initial and final states are favorably trapped by the lattice light,
allowing optimized transfer in agreement with the experimental observation
Resonant Coupling in the Heteronuclear Alkali Dimers for Direct Photoassociative Formation of X(0,0) Ultracold Molecules
Promising pathways for photoassociative formation of ultracold heteronuclear
alkali metal dimers in their lowest rovibronic levels (denoted X(0,0)) are
examined using high quality ab initio calculations of potential energy curves
currently available. A promising pathway for KRb, involving the resonant
coupling of the and states just below the lowest excited
asymptote (K()+Rb()), is found to occur also for RbCs and less
promisingly for KCs as well. The resonant coupling of the and
states, also just below the lowest excited asymptote, is found to be
promising for LiNa, LiK, LiRb, and less promising for LiCs and KCs. Direct
photoassociation to the state near dissociation appears promising in
the final dimers, NaK, NaRb, and NaCs, although detuning more than 100
cm below the lowest excited asymptote may be required.Comment: 20 pages, 12 figures, Submitted to Journal of Physical Chemistry
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