744 research outputs found
Morphological Image Analysis of Quantum Motion in Billiards
Morphological image analysis is applied to the time evolution of the
probability distribution of a quantum particle moving in two and
three-dimensional billiards. It is shown that the time-averaged Euler
characteristic of the probability density provides a well defined quantity to
distinguish between classically integrable and non-integrable billiards. In
three dimensions the time-averaged mean breadth of the probability density may
also be used for this purpose.Comment: Major revision. Changes include a more detailed discussion of the
theory and results for 3 dimensions. Now: 10 pages, 9 figures (some are
colored), 3 table
Event-based simulation of interference with alternatingly blocked particle sources
We analyze the predictions of an event-based corpuscular model for
interference in the case of two-beam interference experiments in which the two
sources are alternatingly blocked. We show that such experiments may be used to
test specific predictions of the corpuscular model.Comment: FPP6 - Foundations of Probability and Physics 6, edited by A.
Khrennikov et al., AIP Conference Proceeding
Coexistence of full which-path information and interference in Wheelers delayed choice experiment with photons
We present a computer simulation model that is a one-to-one copy of an
experimental realization of Wheeler's delayed choice experiment that employs a
single photon source and a Mach-Zehnder interferometer composed of a 50/50
input beam splitter and a variable output beam splitter with adjustable
reflection coefficient (V. Jacques {\sl et al.}, Phys. Rev. Lett. 100,
220402 (2008)). For , experimentally measured values of the
interference visibility and the path distinguishability , a parameter
quantifying the which-path information WPI, are found to fulfill the
complementary relation , thereby allowing to obtain partial WPI
while keeping interference with limited visibility. The simulation model that
is solely based on experimental facts, that satisfies Einstein's criterion of
local causality and that does not rely on any concept of quantum theory or of
probability theory, reproduces quantitatively the averages calculated from
quantum theory. Our results prove that it is possible to give a particle-only
description of the experiment, that one can have full WPI even if D=0, V=1 and
therefore that the relation cannot be regarded as quantifying
the notion of complementarity.Comment: Physica E, in press; see also http://www.compphys.ne
Reply to Comment on "A local realist model for correlations of the singlet state"
The general conclusion of Seevinck and Larsson is that our model exploits the
so-called coincidence-time loophole and produces sinusoidal (quantum-like)
correlations but does not model the singlet state because it does not violate
the relevant Bell inequality derived by Larsson and Gill, since in order to
obtain the sinusoidal correlations the probability of coincidences in our model
goes to zero. In this reply, we refute their arguments that lead to this
conclusion and demonstrate that our model can reproduce results of photon and
ion-trap experiments with frequencies of coincidences that are not in conflict
with the observations.Comment: Corrected typo
Quantum Decoherence at Finite Temperatures
We study measures of decoherence and thermalization of a quantum system
in the presence of a quantum environment (bath) . The whole system is
prepared in a canonical thermal state at a finite temperature. Applying
perturbation theory with respect to the system-environment coupling strength,
we find that under common Hamiltonian symmetries, up to first order in the
coupling strength it is sufficient to consider the uncoupled system to predict
decoherence and thermalization measures of . This decoupling allows closed
form expressions for perturbative expansions for the measures of decoherence
and thermalization in terms of the free energies of and of . Numerical
results for both coupled and decoupled systems with up to 40 quantum spins
validate these findings.Comment: 5 pages, 3 figure
Quantum Spin Dynamics and Quantum Computation
We describe a simulation method for a quantum spin model of a generic,
general purpose quantum computer. The use of this quantum computer simulator is
illustrated through several implementations of Grover's database search
algorithm. Some preliminary results on the stability of quantum algorithms are
presented.Comment: 6 pages, 4 figures ; Minor errors corrected and figures update
Proposal for an interference experiment to test the applicability of quantum theory to event-based processes
We analyze a single-particle Mach-Zehnder interferometer experiment in which
the path length of one arm may change (randomly or systematically) according to
the value of an external two-valued variable , for each passage of a
particle through the interferometer. Quantum theory predicts an interference
pattern that is independent of the sequence of the values of . On the other
hand, corpuscular models that reproduce the results of quantum optics
experiments carried out up to this date show a reduced visibility and a shift
of the interference pattern depending on the details of the sequence of the
values of . The proposed experiment will show that: (1) it can be described
by quantum theory, and thus not by the current corpuscular models, or (2) it
cannot be described by quantum theory but can be described by the corpuscular
models or variations thereof, or (3) it can neither be described by quantum
theory nor by corpuscular models. Therefore, the proposed experiment can be
used to determine to what extent quantum theory provides a description of
observed events beyond the usual statistical level.Comment: Accepted for publication in J. Phys. Soc. Jp
The puzzlingly large Ca II triplet absorption in dwarf elliptical galaxies
We present central CaT, PaT, and CaT* indices for a sample of fifteen dwarf
elliptical galaxies (dEs). Twelve of these have CaT* ~ 7 A and extend the
negative correlation between the CaT* index and central velocity dispersion
sigma, which was derived for bright ellipticals (Es), down to 20 < sigma < 55
km/s. For five dEs we have independent age and metallicity estimates. Four of
these have CaT* ~ 7 A, much higher than expected from their low metallicities
(-1.5 < [Z/H] < -0.5). The observed anti-correlation of CaT* as a function of
sigma or Z is in flagrant disagreement with theory. We discuss some of the
amendments that have been proposed to bring the theoretical predictions into
agreement with the observed CaT*-values of bright Es and how they can be
extended to incorporate also the observed CaT*-values of dEs. Moreover, 3 dEs
in our sample have CaT* ~ 5 A, as would be expected for metal-poor stellar
systems. Any theory for dE evolution will have to be able to explain the
co-existence of low-CaT* and high-CaT* dEs at a given mean metallicity. This
could be the first direct evidence that the dE population is not homogeneous,
and that different evolutionary paths led to morphologically and kinematically
similar but chemically distinct objects.Comment: 4 pages, 3 figures, accepted for publication in ApJ Letter
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