94 research outputs found
High-Dimensional Similarity Search with Quantum-Assisted Variational Autoencoder
Recent progress in quantum algorithms and hardware indicates the potential
importance of quantum computing in the near future. However, finding suitable
application areas remains an active area of research. Quantum machine learning
is touted as a potential approach to demonstrate quantum advantage within both
the gate-model and the adiabatic schemes. For instance, the Quantum-assisted
Variational Autoencoder has been proposed as a quantum enhancement to the
discrete VAE. We extend on previous work and study the real-world applicability
of a QVAE by presenting a proof-of-concept for similarity search in large-scale
high-dimensional datasets. While exact and fast similarity search algorithms
are available for low dimensional datasets, scaling to high-dimensional data is
non-trivial. We show how to construct a space-efficient search index based on
the latent space representation of a QVAE. Our experiments show a correlation
between the Hamming distance in the embedded space and the Euclidean distance
in the original space on the Moderate Resolution Imaging Spectroradiometer
(MODIS) dataset. Further, we find real-world speedups compared to linear search
and demonstrate memory-efficient scaling to half a billion data points
Azimuthal Correlations in the Target Fragmentation Region of High Energy Nuclear Collisions
Results on the target mass dependence of proton and pion pseudorapidity
distributions and of their azimuthal correlations in the target rapidity range
are presented. The data have been taken with the
Plastic-Ball detector set-up for 4.9 GeV p + Au collisions at the Berkeley
BEVALAC and for 200 GeV/ p-, O-, and S-induced reactions on
different nuclei at the CERN-SPS. The yield of protons at backward rapidities
is found to be proportional to the target mass. Although protons show a typical
``back-to-back'' correlations, a ``side-by-side'' correlation is observed for
positive pions, which increases both with target mass and with impact parameter
of a collision. The data can consistently be described by assuming strong
rescattering phenomena including pion absorption effects in the entire excited
target nucleus.Comment: 7 pages, figures included, complete postscript available at
ftp://qgp.uni-muenster.de/pub/paper/azi-correlations.ps submitted to Phys.
Lett.
Finding and testing network communities by lumped Markov chains
Identifying communities (or clusters), namely groups of nodes with
comparatively strong internal connectivity, is a fundamental task for deeply
understanding the structure and function of a network. Yet, there is a lack of
formal criteria for defining communities and for testing their significance. We
propose a sharp definition which is based on a significance threshold. By means
of a lumped Markov chain model of a random walker, a quality measure called
"persistence probability" is associated to a cluster. Then the cluster is
defined as an "-community" if such a probability is not smaller than
. Consistently, a partition composed of -communities is an
"-partition". These definitions turn out to be very effective for
finding and testing communities. If a set of candidate partitions is available,
setting the desired -level allows one to immediately select the
-partition with the finest decomposition. Simultaneously, the
persistence probabilities quantify the significance of each single community.
Given its ability in individually assessing the quality of each cluster, this
approach can also disclose single well-defined communities even in networks
which overall do not possess a definite clusterized structure
Validation of the German version of the STarT-Back Tool (STarT-G): a cohort study with patients from primary care practices
Technical support and delegation to practice staff â status quo and (possible) future perspectives for primary health care in Germany
Azimuthal anisotropy in S+Au reactions at 200 A GeV
Azimuthal correlations of photons produced at mid-rapidity in 200 A GeV S + Au collisions have been studied using a preshower photon multiplicity detector in the WA93 experiment. The Fourier expansion method has been employed to estimate the event plane via the anisotropy of the event as a function of centrality. The event plane correlation technique has been used to determine the true event anisotropy, beyond the anisotropy which arises due to finite multiplicity. The VENUS event generator with rescattering and proper simulation of the detector response can explain only a portion of the observed anisotropy. The residual anisotropy is found to be of the order of 5% for semi-central collisions. This suggests that directed collective flow of the produced particles is present at SPS energies. (C) 1997 Published by Elsevier Science B.V
Plaque-associated microglia in mice with AD-like pathology show increased and heterogeneous voltage-activated currents
Plaqueâdependent morphological and electrophysiological heterogeneity of microglia in an Alzheimer's disease mouse model
Investigation of the properties of a radial silicon drift detector in the WA93-experiment
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