292 research outputs found
Entangled coherent states and squeezing in N trapped ions
We consider a resonant bichromatic excitation of N trapped ions that
generates displacement and squeezing in their collective motion conditioned to
their ionic internal state, producing eventually Scrhodinger cat states and
entangled squeezing. Furthermore, we study the case of tetrachromatic
illumination or producing the so called entangled coherent states in two
motional normal modes.Comment: 4 Revtex pages, no figures. To appear in Proceedings of "Mysteries,
Puzzles and Paradoxes in Quantum Mechanics", Garda Lake, Italy (2001
Reliable teleportation in trapped ions
We study a method for the implementation of a reliable teleportation protocol
(theoretically, 100% of success) of internal states in trapped ions. The
generation of the quantum channel (any of four Bell states) may be done
respecting technical limitations on individual addressing and without claiming
the Lamb-Dicke regime. An adequate Bell analyzer, that transforms unitarily the
Bell basis into a completely disentangled one, is considered. Probable sources
of error and fidelity estimations of the teleportation process are studied.
Finally, we discuss experimental issues, proposing a scenario in which the
present scheme could be implemented.Comment: 8 Latex pages with five (ps,eps) figures included (EPJ style also
included). Accepted for publication in European Physical Journal
Direct measurement of finite-time disentanglement induced by a reservoir
We propose a method for directly probing the dynamics of disentanglement of
an initial two-qubit entangled state, under the action of a reservoir. We show
that it is possible to detect disentanglement, for experimentally realizable
examples of decaying systems, through the measurement of a single observable,
which is invariant throughout the decay. The systems under consideration may
lead to either finite-time or asymptotic disentanglement. A general
prescription for measuring this observable, which yields an operational meaning
to entanglement measures, is proposed, and exemplified for cavity quantum
electrodynamics and trapped ions.Comment: 4 pages, 2 figure
Single observable concurrence measurement without simultaneous copies
We present a protocol that allows us to obtain the concurrence of any two
qubit pure state by performing a minimal and optimal tomography of one of the
subsystems through measuring a single observable of an ancillary four
dimensional qudit. An implementation for a system of trapped ions is also
proposed, which can be achieved with present day experimental techniques.Comment: 4 pages, 1 figur
An analysis of spectra in the Red Rectangle nebula
This paper presents an analysis of a series of spectra in the Red Rectangle
nebula. Only the reddest part of the spectra can safely be attributed to light
from the nebula, and indicates Rayleigh scattering by the gas, in conformity
with the large angles of scattering involved and the proximity of the star. In
the blue, light from HD44179, refracted or scattered in the atmosphere,
dominates the spectra. This paper questions the reliability of ground-based
observations of extended objects in the blue.Comment: 25 figure
Squeezing generation and revivals in a cavity-ion system in contact with a reservoir
We consider a system consisting of a single two-level ion in a harmonic trap,
which is localized inside a non-ideal optical cavity at zero temperature and
subjected to the action of two external lasers. We are able to obtain an
analytical solution for the total density operator of the system and show that
squeezing in the motion of the ion and in the cavity field is generated. We
also show that complete revivals of the states of the motion of the ion and of
the cavity field occur periodically.Comment: 9 pages, 3 figure
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