944 research outputs found
Quantum limits of super-resolution in reconstruction of optical objects
We investigate analytically and numerically the role of quantum fluctuations
in reconstruction of optical objects from diffraction-limited images. Taking as
example of an input object two closely spaced Gaussian peaks we demonstrate
that one can improve the resolution in the reconstructed object over the
classical Rayleigh limit. We show that the ultimate quantum limit of resolution
in such reconstruction procedure is determined not by diffraction but by the
signal-to-noise ratio in the input object. We formulate a quantitative measure
of super-resolution in terms of the optical point-spread function of the
system.Comment: 23 pages, 7 figures. Submitted to Physical Review A e-mail:
[email protected]
Wigner-Yanase skew information as tests for quantum entanglement
A Bell-type inequality is proposed in terms of Wigner-Yanase skew
information, which is quadratic and involves only one local spin observable at
each site. This inequality presents a hierarchic classification of all states
of multipartite quantum systems from separable to fully entangled states, which
is more powerful than the one presented by quadratic Bell inequalities from
two-entangled to fully entangled states. In particular, it is proved that the
inequality provides an exact test to distinguish entangled from nonentangled
pure states of two qubits. Our inequality sheds considerable light on
relationships between quantum entanglement and information theory.Comment: 5 page
Consistent Application of Maximum Entropy to Quantum-Monte-Carlo Data
Bayesian statistics in the frame of the maximum entropy concept has widely
been used for inferential problems, particularly, to infer dynamic properties
of strongly correlated fermion systems from Quantum-Monte-Carlo (QMC) imaginary
time data. In current applications, however, a consistent treatment of the
error-covariance of the QMC data is missing. Here we present a closed Bayesian
approach to account consistently for the QMC-data.Comment: 13 pages, RevTeX, 2 uuencoded PostScript figure
Information metric from a linear sigma model
The idea that a spacetime metric emerges as a Fisher-Rao `information metric'
of instanton moduli space has been examined in several field theories such as
the Yang-Mills theories and nonlinear sigma models. In this brief paper, we
report that the flat Euclidean or Minkowskian metric, rather than an anti-de
Sitter metric that generically emerges from instanton moduli spaces, can be
obtained as the Fisher-Rao metric from a non-trivial solution of the massive
Klein-Gordon field (a linear sigma model). This realization of the flat space
from the simple field theory would be useful to investigate the ideas that
relate the spacetime geometry with the information geometry.Comment: 8 pages, 1 figure, to appear in PR
A Solution to the Problem of Phaseless Mapping for a High-Orbit Space-Ground Radio Interferometer
We consider the problem of mapping with ultra-high angular resolution using a
space-ground radio interferometer with a space antenna in a high orbit,whose
apogee height exceeds the radius of the Earth by a factor of ten. In this case,
a multielement interferometer essentially degenerates into a two-element
interferometer. The degeneracy of the close-phase relations prevents the use of
standard methods for hybrid mapping and self-calibration for the correct
reconstruction of images. We propose a new phaseless mapping method based on
methods for the reconstruction of images in the complete absence of phase
information, using only the amplitudes of the spatial-coherence function of the
source. In connection with this problem, we propose a new method for the
reliable solution of the phase problem, based on optimizing
information-carrying nonlinear functionals, in particular, the Shannon entropy.
Results of simulations of mapping radio sources with various structures with
ultra-high angular resolution in the framework of the RADIOASTRON mission are
presented.Comment: 15 pages, 7 figure
Universal Genotyping in Tuberculosis Control Program, New York City, 2001â2003
Real-time universal genotyping decreased unnecessary treatment
Multifrequency VLBA study of the blazar S5 0716+714 during the active state in 2004 II. Large-scale jet kinematics and the comparison of the different methods of VLBI data imaging as applied to kinematic studies of AGN
We study the jet kinematics of the blazar S5 0716+714 during its active state
in 2003-2004 with multi-epoch VLBI observations. Aims. We present a kinematic
analysis of the large-scale (0-12 mas) jet of 0716+714, based on the results of
six epochs of VLBA monitoring at 5 GHz. Additionally, we compare kinematic
results obtained with two imaging methods based on different deconvolution
algorithms. The blazar 0716+714 has a diffuse large-scale jet and a very faint
bright compact core. Experiments with simulated data showed that the
conventional data reduction procedure based on the CLEAN deconvolution
algorithm does not perform well in restoring this type of structure. This might
be the reason why previous kinematic studies of this source yielded ambiguous
results. In order to obtain accurate kinematics of this source, we
independently applied two imaging techniques to the raw data: the conventional
method, based on difference mapping, which uses CLEAN deconvolution, and the
generalized maximum entropy method (GMEM) realized in the VLBImager package
developed at the Pulkovo Observatory in Russia. The results of both methods
give us a consistent kinematic scenario: the large-scale jet of 0716+714 is
diffuse and stationary. Differences between the inner (0-1 mas) and outer (1-12
mas) regions of the jet in brightness and velocity of the components could be
explained by the bending of the jet, which causes the angle between the jet
direction and the line of sight to change from ~5 deg to ~11 deg. For the
source 0716+714 both methods worked at the limit of their capability.Comment: 13 pages, 7 figures. Accepted for publication in A&A, 201
Sand in the wheels, or oiling the wheels, of international finance? : New Labour's appeal to a 'new Bretton Woods'
Tony Blairâs political instinct typically is to associate himself only with the future. As such, his explicit appeal to âthe pastâ in his references to New Labourâs desire to establish a ânew Bretton Woodsâ is sufficient in itself to arouse some degree of analytical curiosity (see Blair 1998a). The fact that this appeal was made specifically in relation to Bretton Woods is even more interesting. The resonant image of the international economic context established by the original Bretton Woods agreements invokes a style and content of policy-making which Tony Blair typically dismisses as neither economically nor politically consistent with his preferred vision of the future (see Blair 2000c, 2001b)
Credibility and adjustment: gold standards versus currency boards
It is often maintained that currency boards (CBs) and gold standards (GSs) are alike in that they are stringent monetary rules, the two basic features of which are high credibility of monetary authorities and the existence of automatic adjustment (non discretionary) mechanism. This article includes a comparative analysis of these two types of regimes both from the perspective of the sources and mechanisms of generating confidence and credibility, and the elements of operation of the automatic adjustment mechanism. Confidence under the GS is endogenously driven, whereas it is exogenously determined under the CB. CB is a much more asymmetric regime than GS (the adjustment is much to the detriment of peripheral countries) although asymmetry is a typical feature of any monetary regime. The lack of credibility is typical for peripheral countries and cannot be overcome completely even by âhardâ monetary regimes.http://deepblue.lib.umich.edu/bitstream/2027.42/40078/3/wp692.pd
Contribution to understanding the mathematical structure of quantum mechanics
Probabilistic description of results of measurements and its consequences for
understanding quantum mechanics are discussed. It is shown that the basic
mathematical structure of quantum mechanics like the probability amplitudes,
Born rule, commutation and uncertainty relations, probability density current,
momentum operator, rules for including the scalar and vector potentials and
antiparticles can be obtained from the probabilistic description of results of
measurement of the space coordinates and time. Equations of motion of quantum
mechanics, the Klein-Gordon equation, Schrodinger equation and Dirac equation
are obtained from the requirement of the relativistic invariance of the
space-time Fisher information. The limit case of the delta-like probability
densities leads to the Hamilton-Jacobi equation of classical mechanics. Many
particle systems and the postulates of quantum mechanics are also discussed.Comment: 21 page
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