1,154 research outputs found
Quantum harmonic oscillator state synthesis and analysis
Experiments are described in which a single, harmonically bound, beryllium
ion in a Paul trap is put into Fock, thermal, coherent, squeezed, and
Schroedinger cat states. Experimental determinations of the density matrix and
the Wigner function are described. A simple calculation of the decoherence of a
superposition of coherent states due to an external electric field is given.Comment: 13 pages, LaTeX2e, special style file spie.sty included, 11 eps
figures included using epsfig, graphicx, subfigure, floatflt macros. To
appear in Proc. Conf. on Atom Optics, San Jose, CA, Feb. 1997, edited by M.
G. Prentiss and W. D. Phillips, SPIE Proc. # 299
Temporal and causal reasoning in deaf and hearing novice readers
Temporal and causal information in text are crucial in helping the reader form a coherent representation of a narrative. Deaf novice readers are generally poor at processing linguistic markers of causal/temporal information (i.e., connectives), but what is unclear is whether this is indicative of a more general deficit in reasoning about temporal/causal information. In Study 1, 10 deaf and 63 hearing children, matched for comprehension ability and age, were compared on a range of tasks tapping temporal/causal reasoning skills. In Study 2, 20 deaf and 32 hearing children, matched for age but not reading comprehension ability, were compared on revised versions of the tasks. The pattern of performance of the deaf was different from that of the hearing; they had difficulties when temporal and causal reasoning was text-based, but not when it was nonverbal, indicating that their global temporal/causal reasoning skills are comparable with those of their hearing counterparts
Frequency and time standards based on stored ions
The method of ion storage provides a basis for excellent time and frequency standards. This is due to the ability to confine ions for long periods of time without the usual perturbations associated with confinement (e.g., wall shifts). In addition, Doppler effects can be greatly suppressed. The use of stored ions for microwave frequency standards and the future possibilities for an optical frequency standard based on stored ions are addressed
Complementarity and Young's interference fringes from two atoms
The interference pattern of the resonance fluorescence from a J=1/2 to J=1/2
transition of two identical atoms confined in a three-dimensional harmonic
potential is calculated. Thermal motion of the atoms is included. Agreement is
obtained with experiments [Eichmann et al., Phys. Rev. Lett. 70, 2359 (1993)].
Contrary to some theoretical predictions, but in agreement with the present
calculations, a fringe visibility greater than 50% can be observed with
polarization-selective detection. The dependence of the fringe visibility on
polarization has a simple interpretation, based on whether or not it is
possible in principle to determine which atom emitted the photon.Comment: 12 pages, including 7 EPS figures, RevTex. Submitted to Phys. Rev.
Reexamining Black-Body Shifts for Hydrogenlike Ions
We investigate black-body induced energy shifts for low-lying levels of
atomic systems, with a special emphasis on transitions used in current and
planned high-precision experiments on atomic hydrogen and ionized helium.
Fine-structure and Lamb-shift induced black-body shifts are found to increase
with the square of the nuclear charge number, whereas black-body shifts due to
virtual transitions decrease with increasing nuclear charge as the fourth power
of the nuclear charge. We also investigate the decay width acquired by the
ground state of atomic hydrogen, due to interaction with black-body photons.
The corresponding width is due to an instability against excitation to higher
excited atomic levels, and due to black-body induced ionization. These effects
limit the lifetime of even the most fundamental, a priori absolutely stable,
"asymptotic" state of atomic theory, namely the ground state of atomic
hydrogen.Comment: 11 pages; LaTe
Simplified quantum logic with trapped ions
We describe a simplified scheme for quantum logic with a collection of
laser-cooled trapped atomic ions. Building on the scheme of Cirac and Zoller,
we show how the fundamental controlled-NOT gate between a collective mode of
ion motion and the internal states of a single ion can be reduced to a single
laser pulse, and the need for a third auxiliary internal electronic state can
be eliminated.Comment: 8 pages, PostScript, submitted to Physical Review A, Rapid
Communication
An ion ring in a linear multipole trap for optical frequency metrology
A ring crystal of ions trapped in a linear multipole trap is studied as a
basis for an optical frequency standard. The equilibrium conditions and cooling
possibilities are discussed through an analytical model and molecular dynamics
simulations. A configuration which reduces the frequency sensitivity to the
fluctuations of the number of trapped ions is proposed. The systematic shifts
for the electric quadrupole transition of calcium ions are evaluated for this
ring configuration. This study shows that a ring of 10 or 20 ions allows to
reach a short term stability better than for a single ion without introducing
limiting long term fluctuations
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