573 research outputs found
Manipulation of Single Neutral Atoms in Optical Lattices
We analyze a scheme to manipulate quantum states of neutral atoms at
individual sites of optical lattices using focused laser beams. Spatial
distributions of focused laser intensities induce position-dependent energy
shifts of hyperfine states, which, combined with microwave radiation, allow
selective manipulation of quantum states of individual target atoms. We show
that various errors in the manipulation process are suppressed below
with properly chosen microwave pulse sequences and laser parameters. A similar
idea is also applied to measure quantum states of single atoms in optical
lattices.Comment: 5 pages, 3 figure
Coherence properties of an atom laser
We study the coherence properties of an atom laser, which operates by
extracting atoms from a gaseous Bose-Einstein condensate via a two-photon Raman
process, by analyzing a recent experiment. We obtain good agreement with the
experimental data by solving the time-dependent Gross-Pitaevskii equation in
three dimensions both numerically and with a Thomas-Fermi model. The coherence
length is strongly affected by the space-dependent phase developed by the
condensate when the trapping potential is turned off.Comment: 11 pages, 2 Postscript figure
Fast quantum gates for neutral atoms
We propose several schemes for implementing a fast two-qubit quantum gate for neutral atoms with the gate operation time much faster than the time scales associated with the external motion of the atoms in the trapping potential. In our example, the large interaction energy required to perform fast gate operations is provided by the dipole-dipole interaction of atoms excited to low-lying Rydberg states in constant electric fields. A detailed analysis of imperfections of the gate operation is given
Cold collisions between atoms in optical lattices
We have simulated binary collisions between atoms in optical lattices during
Sisyphus cooling. Our Monte Carlo Wave Function simulations show that the
collisions selectively accelerate mainly the hotter atoms in the thermal
ensemble, and thus affect the steady state which one would normally expect to
reach in Sisyphus cooling without collisions.Comment: 4 pages, 1 figur
A single hollow beam optical trap for cold atoms
We present an optical trap for atoms that we have developed for precision
spectroscopy measurements. Cold atoms are captured in a dark region of space
inside a blue-detuned hollow laser beam formed by an axicon. We analyze the
light potential in a ray optics picture and experimentally demonstrate trapping
of laser-cooled metastable xenon atoms.Comment: 12 pages, 8 figure
Photoassociation of sodium in a Bose-Einstein condensate
We report on the formation of ultra-cold Na molecules using single-photon
photoassociation of a Bose-Einstein condensate. The photoassociation rate,
linewidth and light shift of the J=1, vibrational level of the
\mterm{A}{1}{+}{u} molecular bound state have been measured. We find that the
photoassociation rate constant increases linearly with intensity, even where it
is predicted that many-body effects might limit the rate. Our observations are
everywhere in good agreement with a two-body theory having no free parameters.Comment: Fixes to the figures and references. Just the normal human stupidity
type stuff, nothing Earth-shatterin
Plasma Oscillations and Expansion of an Ultracold Neutral Plasma
We report the observation of plasma oscillations in an ultracold neutral
plasma. With this collective mode we probe the electron density distribution
and study the expansion of the plasma as a function of time. For classical
plasma conditions, i.e. weak Coulomb coupling, the expansion is dominated by
the pressure of the electron gas and is described by a hydrodynamic model.
Discrepancies between the model and observations at low temperature and high
density may be due to strong coupling of the electrons.Comment: 4 pages, 4 figures. Accepted Phys. Rev. Let
Ultrastable CO2 Laser Trapping of Lithium Fermions
We demonstrate an ultrastable CO2 laser trap that provides tight confinement
of neutral atoms with negligible optical scattering and minimal laser-noise-
induced heating. Using this method, fermionic 6Li atoms are stored in a 0.4 mK
deep well with a 1/e trap lifetime of 300 sec, consistent with a background
pressure of 10^(-11) Torr. To our knowledge, this is the longest storage time
ever achieved with an all-optical trap, comparable to the best reported
magnetic traps.Comment: 4 pages using REVTeX, 1 eps figur
Atomic collision dynamics in optical lattices
We simulate collisions between two atoms, which move in an optical lattice
under the dipole-dipole interaction. The model describes simultaneously the two
basic dynamical processes, namely the Sisyphus cooling of single atoms, and the
light-induced inelastic collisions between them. We consider the J=1/2 -> J=3/2
laser cooling transition for Cs, Rb and Na. We find that the hotter atoms in a
thermal sample are selectively lost or heated by the collisions, which modifies
the steady state distribution of atomic velocities, reminiscent of the
evaporative cooling process.Comment: 17 pages, 15 figure
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