2,396 research outputs found
Accuracy of B(E2; 0+ -> 2+) transition rates from intermediate-energy Coulomb excitation experiments
The method of intermediate-energy Coulomb excitation has been widely used to
determine absolute B(E2; 0+ -> 2+) quadrupole excitation strengths in exotic
nuclei with even numbers of protons and neutrons. Transition rates measured
with intermediate-energy Coulomb excitation are compared to their respective
adopted values and for the example of 26Mg to the B(E2; 0+ -> 2+) values
obtained with a variety of standard methods. Intermediate-energy Coulomb
excitation is found to have an accuracy comparable to those of long-established
experimental techniques.Comment: to be published in Phys. Rev.
Atom holography
We study the conditions under which atomic condensates can be used as a
recording media and then suggest a reading scheme which allows to reconstruct
an object with atomic reading beam. We show that good recording can be achieved
for flat condensate profiles and for negative detunings between atomic Bohr
frequency and optical field frequency. The resolution of recording dramatically
depends on the relation between the healing length of the condensate and the
spatial frequency contents of the optical fields involved.Comment: 8 pages, 5 figures, Late
Atomic matter wave scanner
We report on the experimental realization of an atom optical device, that
allows scanning of an atomic beam. We used a time-modulated evanescent wave
field above a glass surface to diffract a continuous beam of metastable Neon
atoms at grazing incidence. The diffraction angles and efficiencies were
controlled by the frequency and form of modulation, respectively. With an
optimized shape, obtained from a numerical simulation, we were able to transfer
more than 50% of the atoms into the first order beam, which we were able to
move over a range of 8 mrad.Comment: 4 pages, 4 figure
Wave Packet Echoes in the Motion of Trapped Atoms
We experimentally demonstrate and systematically study the stimulated revival
(echo) of motional wave packet oscillations. For this purpose, we prepare wave
packets in an optical lattice by non-adiabatically shifting the potential and
stimulate their reoccurence by a second shift after a variable time delay. This
technique, analogous to spin echoes, enables one even in the presence of strong
dephasing to determine the coherence time of the wave packets. We find that for
strongly bound atoms it is comparable to the cooling time and much longer than
the inverse of the photon scattering rate
Ground state laser cooling using electromagnetically induced transparency
A laser cooling method for trapped atoms is described which achieves ground
state cooling by exploiting quantum interference in a driven Lambda-shaped
arrangement of atomic levels. The scheme is technically simpler than existing
methods of sideband cooling, yet it can be significantly more efficient, in
particular when several motional modes are involved, and it does not impose
restrictions on the transition linewidth. We study the full quantum mechanical
model of the cooling process for one motional degree of freedom and show that a
rate equation provides a good approximation.Comment: 4 pages, 3 figures; v2: minor modifications to abstract, text and
figure captions; v3: few references added and rearranged; v4: One part
significantly changed, 1 figure removed, new equations; v5: typos corrected,
to appear in PR
Optics with an Atom Laser Beam
We report on the atom optical manipulation of an atom laser beam. Reflection,
focusing and its storage in a resonator are demonstrated. Precise and versatile
mechanical control over an atom laser beam propagating in an inhomogeneous
magnetic field is achieved by optically inducing spin-flips between atomic
ground states with different magnetic moment. The magnetic force acting on the
atoms can thereby be effectively switched on and off. The surface of the atom
optical element is determined by the resonance condition for the spin-flip in
the inhomogeneous magnetic field. A mirror reflectivity of more than 98% is
measured
Chaos assisted tunnelling with cold atoms
In the context of quantum chaos, both theory and numerical analysis predict
large fluctuations of the tunnelling transition probabilities when irregular
dynamics is present at the classical level. We consider here the
non-dissipative quantum evolution of cold atoms trapped in a time-dependent
modulated periodic potential generated by two laser beams. We give some precise
guidelines for the observation of chaos assisted tunnelling between invariant
phase space structures paired by time-reversal symmetry.Comment: submitted to Phys. Rev. E ; 16 pages, 13 figures; figures of better
quality can be found at http://www.phys.univ-tours.fr/~mouchet
Bose-Einstein condensation in quasi2D trapped gases
We discuss BEC in (quasi)2D trapped gases and find that well below the
transition temperature the equilibrium state is a true condensate,
whereas at intermediate temperatures one has a quasicondensate
(condensate with fluctuating phase). The mean-field interaction in a quasi2D
gas is sensitive to the frequency of the (tight) confinement in the
"frozen" direction, and one can switch the sign of the interaction by changing
. Variation of can also reduce the rates of inelastic
processes, which opens prospects for tunable BEC in trapped quasi2D gases.Comment: 4 revtex pages, 1 figure, text is revised, figure improve
Quantum computing implementations with neutral particles
We review quantum information processing with cold neutral particles, that
is, atoms or polar molecules. First, we analyze the best suited degrees of
freedom of these particles for storing quantum information, and then we discuss
both single- and two-qubit gate implementations. We focus our discussion mainly
on collisional quantum gates, which are best suited for atom-chip-like devices,
as well as on gate proposals conceived for optical lattices. Additionally, we
analyze schemes both for cold atoms confined in optical cavities and hybrid
approaches to entanglement generation, and we show how optimal control theory
might be a powerful tool to enhance the speed up of the gate operations as well
as to achieve high fidelities required for fault tolerant quantum computation.Comment: 19 pages, 12 figures; From the issue entitled "Special Issue on
Neutral Particles
Shape Coexistence and the Effective Nucleon-Nucleon Interaction
The phenomenon of shape coexistence is discussed within the self-consistent
Hartree-Fock method and the nuclear shell model. The occurrence of the
coexisting configurations with different intrinsic shapes is traced back to the
properties of the effective Hamiltonian.Comment: 40 pages (16 text, 24 figures). The file may also be retrieved at
http://csep2.phy.ornl.gov/theory_group/people/dean/shape_coex/shapes.htm
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