53,279 research outputs found
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
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
Analysis of hadronic invariant mass spectrum in inclusive charmless semileptonic B decays
We make an analysis of the hadronic invariant mass spectrum in inclusive
charmless semileptonic B meson decays in a QCD-based approach. The decay width
is studied as a function of the invariant mass cut. We examine their
sensitivities to the parameters of the theory. The theoretical uncertainties in
the determination of from the hadronic invariant mass spectrum are
investigated. A strategy for improving the theoretical accuracy in the value of
is described.Comment: 13 pages, 5 Postscript figure
- …