1,733 research outputs found
Microwave apparatus for gravitational waves observation
In this report the theoretical and experimental activities for the
development of superconducting microwave cavities for the detection of
gravitational waves are presented.Comment: 42 pages, 28 figure
Fitting Jump Models
We describe a new framework for fitting jump models to a sequence of data.
The key idea is to alternate between minimizing a loss function to fit multiple
model parameters, and minimizing a discrete loss function to determine which
set of model parameters is active at each data point. The framework is quite
general and encompasses popular classes of models, such as hidden Markov models
and piecewise affine models. The shape of the chosen loss functions to minimize
determine the shape of the resulting jump model.Comment: Accepted for publication in Automatic
SymmetryGAN: Symmetry Discovery with Deep Learning
What are the symmetries of a dataset? Whereas the symmetries of an individual
data element can be characterized by its invariance under various
transformations, the symmetries of an ensemble of data elements are ambiguous
due to Jacobian factors introduced while changing coordinates. In this paper,
we provide a rigorous statistical definition of the symmetries of a dataset,
which involves inertial reference densities, in analogy to inertial frames in
classical mechanics. We then propose SymmetryGAN as a novel and powerful
approach to automatically discover symmetries using a deep learning method
based on generative adversarial networks (GANs). When applied to Gaussian
examples, SymmetryGAN shows excellent empirical performance, in agreement with
expectations from the analytic loss landscape. SymmetryGAN is then applied to
simulated dijet events from the Large Hadron Collider (LHC) to demonstrate the
potential utility of this method in high energy collider physics applications.
Going beyond symmetry discovery, we consider procedures to infer the underlying
symmetry group from empirical data.Comment: 19 pages, 17 figure
Biological evolution through mutation, selection, and drift: An introductory review
Motivated by present activities in (statistical) physics directed towards
biological evolution, we review the interplay of three evolutionary forces:
mutation, selection, and genetic drift. The review addresses itself to
physicists and intends to bridge the gap between the biological and the
physical literature. We first clarify the terminology and recapitulate the
basic models of population genetics, which describe the evolution of the
composition of a population under the joint action of the various evolutionary
forces. Building on these foundations, we specify the ingredients explicitly,
namely, the various mutation models and fitness landscapes. We then review
recent developments concerning models of mutational degradation. These predict
upper limits for the mutation rate above which mutation can no longer be
controlled by selection, the most important phenomena being error thresholds,
Muller's ratchet, and mutational meltdowns. Error thresholds are deterministic
phenomena, whereas Muller's ratchet requires the stochastic component brought
about by finite population size. Mutational meltdowns additionally rely on an
explicit model of population dynamics, and describe the extinction of
populations. Special emphasis is put on the mutual relationship between these
phenomena. Finally, a few connections with the process of molecular evolution
are established.Comment: 62 pages, 6 figures, many reference
Quantum machine learning: a classical perspective
Recently, increased computational power and data availability, as well as
algorithmic advances, have led machine learning techniques to impressive
results in regression, classification, data-generation and reinforcement
learning tasks. Despite these successes, the proximity to the physical limits
of chip fabrication alongside the increasing size of datasets are motivating a
growing number of researchers to explore the possibility of harnessing the
power of quantum computation to speed-up classical machine learning algorithms.
Here we review the literature in quantum machine learning and discuss
perspectives for a mixed readership of classical machine learning and quantum
computation experts. Particular emphasis will be placed on clarifying the
limitations of quantum algorithms, how they compare with their best classical
counterparts and why quantum resources are expected to provide advantages for
learning problems. Learning in the presence of noise and certain
computationally hard problems in machine learning are identified as promising
directions for the field. Practical questions, like how to upload classical
data into quantum form, will also be addressed.Comment: v3 33 pages; typos corrected and references adde
Optimal asymptotic cloning machines
We pose the question whether the asymptotic equivalence between quantum
cloning and quantum state estimation, valid at the single-clone level, still
holds when all clones are examined globally. We conjecture that the answer is
affirmative and present a large amount of evidence supporting our conjecture,
developing techniques to derive optimal asymptotic cloners and proving their
equivalence with estimation in virtually all scenarios considered in the
literature. Our analysis covers the case of arbitrary finite sets of states,
arbitrary families of coherent states, arbitrary phase- and
multiphase-covariant sets of states, and two-qubit maximally entangled states.
In all these examples we observe that the optimal asymptotic fidelity enjoys a
universality property, as its scaling does not depend on the specific details
of the set of input states, but only on the number of parameters needed to
specify them.Comment: 27 + 9 pages, corrected one observation about cloning of maximally
entangled state
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