7,363 research outputs found
Spin correlated interferometry for polarized and unpolarized photons on a beam splitter
Spin interferometry of the 4th order for independent polarized as well as
unpolarized photons arriving simultaneously at a beam splitter and exhibiting
spin correlation while leaving it, is formulated and discussed in the quantum
approach. Beam splitter is recognized as a source of genuine singlet photon
states. Also, typical nonclassical beating between photons taking part in the
interference of the 4th order is given a polarization dependent explanation.Comment: RevTeX, 19 pages, 1 ps figure, author web page at
http://m3k.grad.hr/pavici
Dispersion and fidelity in quantum interferometry
We consider Mach-Zehnder and Hong-Ou-Mandel interferometers with nonclassical
states of light as input, and study the effect that dispersion inside the
interferometer has on the sensitivity of phase measurements. We study in detail
a number of different one- and two-photon input states, including Fock, dual
Fock, N00N states, and photon pairs from parametric downconversion. Assuming
there is a phase shift in one arm of the interferometer, we compute
the probabilities of measurement outcomes as a function of , and then
compute the Shannon mutual information between and the measurements.
This provides a means of quantitatively comparing the utility of various input
states for determining the phase in the presence of dispersion. In addition, we
consider a simplified model of parametric downconversion for which
probabilities can be explicitly computed analytically, and which serves as a
limiting case of the more realistic downconversion model.Comment: 12 pages, 14 figures. Submitted to Physical Review
Electrical phase change of CVD-grown Ge-Sb-Te thin film device
A prototype Ge-Sb-Te thin film phase-change memory device has been fabricated and reversible threshold and phase change switching demonstrated electrically, with a threshold voltage of 1.5 – 1.7 V. The Ge-Sb-Te thin film was fabricated by chemical vapour deposition (CVD) at atmospheric pressure using GeCl4, SbCl5, and Te precursors with reactive gas H2 at reaction temperature 780 °C and substrate temperature 250 °C. The surface morphology and composition of the CVD-grown Ge-Sb-Te thin film has been characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The CVD-grown Ge-Sb-Te thin film shows promise for the phase change memory applications
Comparisons and Applications of Four Independent Numerical Approaches for Linear Gyrokinetic Drift Modes
To help reveal the complete picture of linear kinetic drift modes, four
independent numerical approaches, based on integral equation, Euler initial
value simulation, Euler matrix eigenvalue solution and Lagrangian particle
simulation, respectively, are used to solve the linear gyrokinetic
electrostatic drift modes equation in Z-pinch with slab simplification and in
tokamak with ballooning space coordinate. We identify that these approaches can
yield the same solution with the difference smaller than 1\%, and the
discrepancies mainly come from the numerical convergence, which is the first
detailed benchmark of four independent numerical approaches for gyrokinetic
linear drift modes. Using these approaches, we find that the entropy mode and
interchange mode are on the same branch in Z-pinch, and the entropy mode can
have both electron and ion branches. And, at strong gradient, more than one
eigenstate of the ion temperature gradient mode (ITG) can be unstable and the
most unstable one can be on non-ground eigenstates. The propagation of ITGs
from ion to electron diamagnetic direction at strong gradient is also observed,
which implies that the propagation direction is not a decisive criterion for
the experimental diagnosis of turbulent mode at the edge plasmas.Comment: 12 pages, 10 figures, accept by Physics of Plasma
Reversible Embedding to Covers Full of Boundaries
In reversible data embedding, to avoid overflow and underflow problem, before
data embedding, boundary pixels are recorded as side information, which may be
losslessly compressed. The existing algorithms often assume that a natural
image has little boundary pixels so that the size of side information is small.
Accordingly, a relatively high pure payload could be achieved. However, there
actually may exist a lot of boundary pixels in a natural image, implying that,
the size of side information could be very large. Therefore, when to directly
use the existing algorithms, the pure embedding capacity may be not sufficient.
In order to address this problem, in this paper, we present a new and efficient
framework to reversible data embedding in images that have lots of boundary
pixels. The core idea is to losslessly preprocess boundary pixels so that it
can significantly reduce the side information. Experimental results have shown
the superiority and applicability of our work
Magnetic Interaction between Surface Engineered Rare-earth Atomic Spins
We report the ab initio study of rare-earth adatoms (Gd) on an insulating
surface. This surface is of interest because of previous studies by scanning
tunneling microscopy showing spin excitations of transition metal adatoms. The
present work is the first study of rare-earth spin-coupled adatoms, as well as
the geometry effect of spin coupling, and the underlying mechanism of
ferromagnetic coupling. The exchange coupling between Gd atoms on the surface
is calculated to be antiferromagnetic in a linear geometry and ferromagnetic in
a diagonal geometry, by considering their collinear spins and using the PBE+U
exchange correlation. We also find the Gd dimers in these two geometries are
similar to the nearest-neighbor (NN) and the next-NN Gd atoms in GdN bulk. We
analyze how much direct exchange, superexchange, and RKKY interactions
contribute to the exchange coupling for both geometries by additional
first-principles calculations of related model systems
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