3,176 research outputs found
Lyapunov Generation of Entanglement and the Correspondence Principle
We show how a classically vanishing interaction generates entanglement
between two initially nonentangled particles, without affecting their classical
dynamics. For chaotic dynamics, the rate of entanglement is shown to saturate
at the Lyapunov exponent of the classical dynamics as the interaction strength
increases. In the saturation regime, the one-particle Wigner function follows
classical dynamics better and better as one goes deeper and deeper in the
semiclassical limit. This demonstrates that quantum-classical correspondence at
the microscopic level requires neither high temperatures, nor coupling to a
large number of external degrees of freedom
Long-Time Coherence in Echo Spectroscopy with ---- Pulse Sequence
Motivated by atom optics experiments, we investigate a new class of fidelity
functions describing the reconstruction of quantum states by time-reversal
operations as . We show that the decay of
is quartic in time at short times, and that it freezes well
above the ergodic value at long times, when is not too large. The
long-time saturation value of contains easily extractable
information on the strength of decoherence in these systems.Comment: 5 pages, 3 figure
Decoherence: Concepts and Examples
We give a pedagogical introduction to the process of decoherence - the
irreversible emergence of classical properties through interaction with the
environment. After discussing the general concepts, we present the following
examples: Localisation of objects, quantum Zeno effect, classicality of fields
and charges in QED, and decoherence in gravity theory. We finally emphasise the
important interpretational features of decoherence.Comment: 24 pages, LATEX, 9 figures, needs macro lamuphys.sty, to appear in
the Proceedings of the 10th Born Symposiu
Dynamics of Global Entanglement under Decoherence
We investigate the dynamics of global entanglement, the Meyer-Wallach
measure, under decoherence, analytically. We study two important class of
multi-partite entangled states, the Greenberger-Horne-Zeilinger and the W
state. We obtain exact results for various models of system-environment
interactions (decoherence). Our results shows distinctly different scaling
behavior for these initially entangled states indicating a relative robustness
of the W state, consistent with previous studies.Comment: 5 pages and 5 figure
Localization of Relative-Position of Two Atoms Induced by Spontaneous Emission
We revisit the back-action of emitted photons on the motion of the relative
position of two cold atoms. We show that photon recoil resulting from the
spontaneous emission can induce the localization of the relative position of
the two atoms through the entanglement between the spatial motion of individual
atoms and their emitted photons. The result provides a more realistic model for
the analysis of the environment-induced localization of a macroscopic object.Comment: 8 pages and 4 figure
The General Correlation Function in the Schwinger Model on a Torus
In the framework of the Euclidean path integral approach we derive the exact
formula for the general N-point chiral densities correlator in the Schwinger
model on a torusComment: 17 pages, misprints corrected, references adde
Quantum particles from coarse grained classical probabilities in phase space
Quantum particles can be obtained from a classical probability distribution
in phase space by a suitable coarse graining, whereby simultaneous classical
information about position and momentum can be lost. For a suitable time
evolution of the classical probabilities and choice of observables all features
of a quantum particle in a potential follow from classical statistics. This
includes interference, tunneling and the uncertainty relation.Comment: 19 page
Frame Combination Techniques for Ultra High-Contrast Imaging
We summarize here an experimental frame combination pipeline we developed for
ultra high-contrast imaging with systems like the upcoming VLT SPHERE
instrument. The pipeline combines strategies from the Drizzle technique, the
Spitzer IRACproc package, and homegrown codes, to combine image sets that may
include a rotating field of view and arbitrary shifts between frames. The
pipeline is meant to be robust at dealing with data that may contain non-ideal
effects like sub-pixel pointing errors, missing data points, non-symmetrical
noise sources, arbitrary geometric distortions, and rapidly changing point
spread functions. We summarize in this document individual steps and
strategies, as well as results from preliminary tests and simulations.Comment: 9 pages, 4 figures, SPIE conference pape
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