5,112 research outputs found
Differential Evolution for Many-Particle Adaptive Quantum Metrology
We devise powerful algorithms based on differential evolution for adaptive
many-particle quantum metrology. Our new approach delivers adaptive quantum
metrology policies for feedback control that are orders-of-magnitude more
efficient and surpass the few-dozen-particle limitation arising in methods
based on particle-swarm optimization. We apply our method to the
binary-decision-tree model for quantum-enhanced phase estimation as well as to
a new problem: a decision tree for adaptive estimation of the unknown bias of a
quantum coin in a quantum walk and show how this latter case can be realized
experimentally.Comment: Fig. 2(a) is the cover of Physical Review Letters Vol. 110 Issue 2
Finite-size scaling of pseudo-critical point distributions in the random transverse-field Ising chain
We study the distribution of finite size pseudo-critical points in a
one-dimensional random quantum magnet with a quantum phase transition described
by an infinite randomness fixed point. Pseudo-critical points are defined in
three different ways: the position of the maximum of the average entanglement
entropy, the scaling behavior of the surface magnetization, and the energy of a
soft mode. All three lead to a log-normal distribution of the pseudo-critical
transverse fields, where the width scales as with and the
shift of the average value scales as with ,
which we related to the scaling of average and typical quantities in the
critical region.Comment: 4 pages, 2 figure
CT Angiography in Ischemic Stroke: Optimization and Accuracy
Stroke is the third leading cause of death after coronary heart disease and cancer.
The clinical burden of stroke now exceeds that of coronary heart disease.1 Especially
in the aging population stroke is a major disease. By the year 2020 the incidence
of stroke in the Netherlands is expected to have increased to 2.5 per 1000 and the
prevalence to 8.7 per 1000 for the whole population.2 Stroke is also the most common
cause of disabilities in adults. Therefore not only the disease impact but also
the healthcare impact of stroke is substantial.3
Stroke is defined as the clinical syndrome of rapid onset of focal or global cerebral
deficit with a presumed vascular cause. Different pathological mechanisms can be
responsible for a stroke: cerebral ischemia (≈80%), primary intracerebral hemorrhage
(≈15%), and subarachnoid hemorrhage (≈5%). Ischemic stroke is confined to
an area of the brain perfused by a specific artery and lasts longer than 24 hours or
has led to death. Transient ischemic attack (TIA) is a brief episode of neurological
dysfunction caused by focal brain or retinal ischemia, with clinical symptoms usually
lasting less than 24 hours, and without evidence of acute infarction
Probing the tails of the ground state energy distribution for the directed polymer in a random medium of dimension via a Monte-Carlo procedure in the disorder
In order to probe with high precision the tails of the ground-state energy
distribution of disordered spin systems, K\"orner, Katzgraber and Hartmann
\cite{Ko_Ka_Ha} have recently proposed an importance-sampling Monte-Carlo
Markov chain in the disorder. In this paper, we combine their Monte-Carlo
procedure in the disorder with exact transfer matrix calculations in each
sample to measure the negative tail of ground state energy distribution
for the directed polymer in a random medium of dimension .
In , we check the validity of the algorithm by a direct comparison with
the exact result, namely the Tracy-Widom distribution. In dimensions and
, we measure the negative tail up to ten standard deviations, which
correspond to probabilities of order . Our results are
in agreement with Zhang's argument, stating that the negative tail exponent
of the asymptotic behavior
as is directly related to the fluctuation exponent
(which governs the fluctuations
of the ground state energy for polymers of length ) via the simple
formula . Along the paper, we comment on the
similarities and differences with spin-glasses.Comment: 13 pages, 16 figure
Numerical study of the disordered Poland-Scheraga model of DNA denaturation
We numerically study the binary disordered Poland-Scheraga model of DNA
denaturation, in the regime where the pure model displays a first order
transition (loop exponent ). We use a Fixman-Freire scheme for the
entropy of loops and consider chain length up to , with
averages over samples. We present in parallel the results of various
observables for two boundary conditions, namely bound-bound (bb) and
bound-unbound (bu), because they present very different finite-size behaviors,
both in the pure case and in the disordered case. Our main conclusion is that
the transition remains first order in the disordered case: in the (bu) case,
the disorder averaged energy and contact densities present crossings for
different values of without rescaling. In addition, we obtain that these
disorder averaged observables do not satisfy finite size scaling, as a
consequence of strong sample to sample fluctuations of the pseudo-critical
temperature. For a given sample, we propose a procedure to identify its
pseudo-critical temperature, and show that this sample then obeys first order
transition finite size scaling behavior. Finally, we obtain that the disorder
averaged critical loop distribution is still governed by in
the regime , as in the pure case.Comment: 12 pages, 13 figures. Revised versio
ACVIM consensus statement guidelines for the diagnosis, classification, treatment, and monitoring of pulmonary hypertension in dogs.
Pulmonary hypertension (PH), defined by increased pressure within the pulmonary vasculature, is a hemodynamic and pathophysiologic state present in a wide variety of cardiovascular, respiratory, and systemic diseases. The purpose of this consensus statement is to provide a multidisciplinary approach to guidelines for the diagnosis, classification, treatment, and monitoring of PH in dogs. Comprehensive evaluation including consideration of signalment, clinical signs, echocardiographic parameters, and results of other diagnostic tests supports the diagnosis of PH and allows identification of associated underlying conditions. Dogs with PH can be classified into the following 6 groups: group 1, pulmonary arterial hypertension; group 2, left heart disease; group 3, respiratory disease/hypoxia; group 4, pulmonary emboli/pulmonary thrombi/pulmonary thromboemboli; group 5, parasitic disease (Dirofilaria and Angiostrongylus); and group 6, disorders that are multifactorial or with unclear mechanisms. The approach to treatment of PH focuses on strategies to decrease the risk of progression, complications, or both, recommendations to target underlying diseases or factors contributing to PH, and PH-specific treatments. Dogs with PH should be monitored for improvement, static condition, or progression, and any identified underlying disorder should be addressed and monitored simultaneously
Random walk in a two-dimensional self-affine random potential : properties of the anomalous diffusion phase at small external force
We consider the random walk of a particle in a two-dimensional self-affine
random potential of Hurst exponent in the presence of an external force
. We present numerical results on the statistics of first-passage times that
satisfy closed backward master equations. We find that there exists a
zero-velocity phase in a finite region of the external force , where
the dynamics follows the anomalous diffusion law $ x(t) \sim \xi(F) \
t^{\mu(F)} 0<\mu(F)<1\xi(F)FF \to 0\mu(F) \propto F^aa \simeq 0.6a=1d=1\xi(F) \propto F^{-\nu}\nu
\simeq 1.29\nu=2d=1\xi(F)1/\mu(F)d=1$,
means that the particle uses the transverse direction to find lower barriers.Comment: 10 pages, 8 figures, v2=final versio
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