1,883 research outputs found
Hybrid Quantum-Classical Generative Adversarial Network for High Resolution Image Generation
Quantum machine learning (QML) has received increasing attention due to its
potential to outperform classical machine learning methods in problems
pertaining classification and identification tasks. A subclass of QML methods
is quantum generative adversarial networks (QGANs) which have been studied as a
quantum counterpart of classical GANs widely used in image manipulation and
generation tasks. The existing work on QGANs is still limited to small-scale
proof-of-concept examples based on images with significant downscaling. Here we
integrate classical and quantum techniques to propose a new hybrid
quantum-classical GAN framework. We demonstrate its superior learning
capabilities by generating pixels grey-scale images without
dimensionality reduction or classical pre/post-processing on multiple classes
of the standard MNIST and Fashion MNIST datasets, which achieves comparable
results to classical frameworks with three orders of magnitude less trainable
generator parameters. To gain further insight into the working of our hybrid
approach, we systematically explore the impact of its parameter space by
varying the number of qubits, the size of image patches, the number of layers
in the generator, the shape of the patches and the choice of prior
distribution. Our results show that increasing the quantum generator size
generally improves the learning capability of the network. The developed
framework provides a foundation for future design of QGANs with optimal
parameter set tailored for complex image generation tasks
Benchmarking Adversarially Robust Quantum Machine Learning at Scale
Machine learning (ML) methods such as artificial neural networks are rapidly
becoming ubiquitous in modern science, technology and industry. Despite their
accuracy and sophistication, neural networks can be easily fooled by carefully
designed malicious inputs known as adversarial attacks. While such
vulnerabilities remain a serious challenge for classical neural networks, the
extent of their existence is not fully understood in the quantum ML setting. In
this work, we benchmark the robustness of quantum ML networks, such as quantum
variational classifiers (QVC), at scale by performing rigorous training for
both simple and complex image datasets and through a variety of high-end
adversarial attacks. Our results show that QVCs offer a notably enhanced
robustness against classical adversarial attacks by learning features which are
not detected by the classical neural networks, indicating a possible quantum
advantage for ML tasks. Contrarily, and remarkably, the converse is not true,
with attacks on quantum networks also capable of deceiving classical neural
networks. By combining quantum and classical network outcomes, we propose a
novel adversarial attack detection technology. Traditionally quantum advantage
in ML systems has been sought through increased accuracy or algorithmic
speed-up, but our work has revealed the potential for a new kind of quantum
advantage through superior robustness of ML models, whose practical realisation
will address serious security concerns and reliability issues of ML algorithms
employed in a myriad of applications including autonomous vehicles,
cybersecurity, and surveillance robotic systems.Comment: 10 pages, 5 Figure
Drastic Circuit Depth Reductions with Preserved Adversarial Robustness by Approximate Encoding for Quantum Machine Learning
Quantum machine learning (QML) is emerging as an application of quantum
computing with the potential to deliver quantum advantage, but its realisation
for practical applications remains impeded by challenges. Amongst those, a key
barrier is the computationally expensive task of encoding classical data into a
quantum state, which could erase any prospective speed-ups over classical
algorithms. In this work, we implement methods for the efficient preparation of
quantum states representing encoded image data using variational, genetic and
matrix product state based algorithms. Our results show that these methods can
approximately prepare states to a level suitable for QML using circuits two
orders of magnitude shallower than a standard state preparation implementation,
obtaining drastic savings in circuit depth and gate count without unduly
sacrificing classification accuracy. Additionally, the QML models trained and
evaluated on approximately encoded data display an increased robustness to
adversarially generated input data perturbations. This partial alleviation of
adversarial vulnerability, possible due to the "drowning out" of adversarial
perturbations while retaining the meaningful large-scale features of the data,
constitutes a considerable benefit for approximate state preparation in
addition to lessening the requirements of the quantum hardware. Our results,
based on simulations and experiments on IBM quantum devices, highlight a
promising pathway for the future implementation of accurate and robust QML
models on complex datasets relevant for practical applications, bringing the
possibility of NISQ-era QML advantage closer to reality.Comment: 14 pages, 8 figure
Towards quantum enhanced adversarial robustness in machine learning
Machine learning algorithms are powerful tools for data driven tasks such as
image classification and feature detection, however their vulnerability to
adversarial examples - input samples manipulated to fool the algorithm -
remains a serious challenge. The integration of machine learning with quantum
computing has the potential to yield tools offering not only better accuracy
and computational efficiency, but also superior robustness against adversarial
attacks. Indeed, recent work has employed quantum mechanical phenomena to
defend against adversarial attacks, spurring the rapid development of the field
of quantum adversarial machine learning (QAML) and potentially yielding a new
source of quantum advantage. Despite promising early results, there remain
challenges towards building robust real-world QAML tools. In this review we
discuss recent progress in QAML and identify key challenges. We also suggest
future research directions which could determine the route to practicality for
QAML approaches as quantum computing hardware scales up and noise levels are
reduced.Comment: 10 Pages, 4 Figure
Relating Physical Observables in QCD without Scale-Scheme Ambiguity
We discuss the St\"uckelberg-Peterman extended renormalization group
equations in perturbative QCD, which express the invariance of physical
observables under renormalization-scale and scheme-parameter transformations.
We introduce a universal coupling function that covers all possible choices of
scale and scheme. Any perturbative series in QCD is shown to be equivalent to a
particular point in this function. This function can be computed from a set of
first-order differential equations involving the extended beta functions. We
propose the use of these evolution equations instead of perturbative series for
numerical evaluation of physical observables. This formalism is free of
scale-scheme ambiguity and allows a reliable error analysis of higher-order
corrections. It also provides a precise definition for as the pole in the associated 't Hooft scheme. A concrete application to
is presented.Comment: Plain TEX, 4 figures (available upon request), 22 pages,
DOE/ER/40322-17
Trends in Weekly Reported Net use by Children During and after Rainy Season in Central Tanzania.
The use of long-lasting insecticidal nets (LLINs) is one of the principal interventions to prevent malaria in young children, reducing episodes of malaria by 50% and child deaths by one fifth. Prioritizing young children for net use is important to achieve mortality reductions, particularly during transmission seasons. Households were followed up weekly from January through June 2009 to track net use among children under seven under as well as caretakers. Net use rates for children and caretakers in net-owning households were calculated by dividing the number of person-weeks of net use by the number of person-weeks of follow-up. Use was stratified by age of the child or caretaker status. Determinants of ownership and of use were assessed using multivariate models. Overall, 60.1% of the households reported owning a bed net at least once during the study period. Among net owners, use rates remained high during and after the rainy season. Rates of use per person-week decreased as the age of the child rose from 0 to six years old; at ages 0-23 months and 24-35 months use rates per person-week were 0.93 and 0.92 respectively during the study period, while for children ages 3 and 4 use rates per person-week were 0.86 and 0.80. For children ages 5-6 person-week ratios dropped to 0.55. This represents an incidence rate ratio of 1.67 for children ages 0-23 months compared to children aged 5-6. Caretakers had use rates similar to those of children age 0-35 months. Having fewer children under age seven in the household also appeared to positively impact net use rates for individual children. In this area of Tanzania, net use is very high among net-owning households, with no variability either at the beginning or end of the rainy season high transmission period. The youngest children are prioritized for sleeping under the net and caretakers also have high rates of use. Given the high use rates, increasing the number of nets available in the household is likely to boost use rates by older children
Correlates of Cooperation in a One-Shot High-Stakes Televised Prisoners' Dilemma
Explaining cooperation between non-relatives is a puzzle for both evolutionary biology and the social sciences. In humans, cooperation is often studied in a laboratory setting using economic games such as the prisoners' dilemma. However, such experiments are sometimes criticized for being played for low stakes and by misrepresentative student samples. Golden balls is a televised game show that uses the prisoners' dilemma, with a diverse range of participants, often playing for very large stakes. We use this non-experimental dataset to investigate the factors that influence cooperation when “playing” for considerably larger stakes than found in economic experiments. The game show has earlier stages that allow for an analysis of lying and voting decisions. We found that contestants were sensitive to the stakes involved, cooperating less when the stakes were larger in both absolute and relative terms. We also found that older contestants were more likely to cooperate, that liars received less cooperative behavior, but only if they told a certain type of lie, and that physical contact was associated with reduced cooperation, whereas laughter and promises were reliable signals or cues of cooperation, but were not necessarily detected
GMD perspective: The quest to improve the evaluation of groundwater representation in continental- to global-scale models
Continental- to global-scale hydrologic and land surface models increasingly include representations of the groundwater system. Such large-scale models are essential for examining, communicating, and understanding the dynamic interactions between the Earth system above and below the land surface as well as the opportunities and limits of groundwater resources. We argue that both large-scale and regional-scale groundwater models have utility, strengths, and limitations, so continued modeling at both scales is essential and mutually beneficial. A crucial quest is how to evaluate the realism, capabilities, and performance of large-scale groundwater models given their modeling purpose of addressing large-scale science or sustainability questions as well as limitations in data availability and commensurability. Evaluation should identify if, when, or where large-scale models achieve their purpose or where opportunities for improvements exist so that such models better achieve their purpose. We suggest that reproducing the spatiotemporal details of regional-scale models and matching local data are not relevant goals. Instead, it is important to decide on reasonable model expectations regarding when a large-scale model is performing “well enough” in the context of its specific purpose. The decision of reasonable expectations is necessarily subjective even if the evaluation criteria are quantitative. Our objective is to provide recommendations for improving the evaluation of groundwater representation in continental- to global-scale models. We describe current modeling strategies and evaluation practices, and we subsequently discuss the value of three evaluation strategies: (1) comparing model outputs with available observations of groundwater levels or other state or flux variables (observation-based evaluation), (2) comparing several models with each other with or without reference to actual observations (model-based evaluation), and (3) comparing model behavior with expert expectations of hydrologic behaviors in particular regions or at particular times (expert-based evaluation). Based on evolving practices in model evaluation as well as innovations in observations, machine learning, and expert elicitation, we argue that combining observation-, model-, and expert-based model evaluation approaches, while accounting for commensurability issues, may significantly improve the realism of groundwater representation in large-scale models, thus advancing our ability for quantification, understanding, and prediction of crucial Earth science and sustainability problems. We encourage greater community-level communication and cooperation on this quest, including among global hydrology and land surface modelers, local to regional hydrogeologists, and hydrologists focused on model development and evaluation
Strong Interaction Physics at the Luminosity Frontier with 22 GeV Electrons at Jefferson Lab
This document presents the initial scientific case for upgrading the
Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab)
to 22 GeV. It is the result of a community effort, incorporating insights from
a series of workshops conducted between March 2022 and April 2023. With a track
record of over 25 years in delivering the world's most intense and precise
multi-GeV electron beams, CEBAF's potential for a higher energy upgrade
presents a unique opportunity for an innovative nuclear physics program, which
seamlessly integrates a rich historical background with a promising future. The
proposed physics program encompass a diverse range of investigations centered
around the nonperturbative dynamics inherent in hadron structure and the
exploration of strongly interacting systems. It builds upon the exceptional
capabilities of CEBAF in high-luminosity operations, the availability of
existing or planned Hall equipment, and recent advancements in accelerator
technology. The proposed program cover various scientific topics, including
Hadron Spectroscopy, Partonic Structure and Spin, Hadronization and Transverse
Momentum, Spatial Structure, Mechanical Properties, Form Factors and Emergent
Hadron Mass, Hadron-Quark Transition, and Nuclear Dynamics at Extreme
Conditions, as well as QCD Confinement and Fundamental Symmetries. Each topic
highlights the key measurements achievable at a 22 GeV CEBAF accelerator.
Furthermore, this document outlines the significant physics outcomes and unique
aspects of these programs that distinguish them from other existing or planned
facilities. In summary, this document provides an exciting rationale for the
energy upgrade of CEBAF to 22 GeV, outlining the transformative scientific
potential that lies within reach, and the remarkable opportunities it offers
for advancing our understanding of hadron physics and related fundamental
phenomena.Comment: Updates to the list of authors; Preprint number changed from theory
to experiment; Updates to sections 4 and 6, including additional figure
Perturbative QCD Calculations of Total Cross Sections and Decay Widths in Hard Inclusive Processes
A summary of the current understanding of methods of analytical higher order
perturbative computations of total cross sections and decay widths in Quantum
Chromodynamics is presented. As examples, the total cross section in electron
positron annihilation, the hadronic decay rates of the tau lepton and Higgs
boson up to O(\alpha_s^2) and O(\alpha_s^3) are considered. The evaluation of
the four-loop QED \beta - function at an intermediate step of the calculation
is briefly described. The problem of renormalization group ambiguity of
perturbative results is considered and some of the existing prescriptions are
discussed. The problem of estimation of theoretical uncertainty in perturbative
calculations is briefly discussed.Comment: 83 pages, LaTeX, Reviews of Modern Physics style, 14 figures plus
figural equations (not included). Hard copy available upon request at
[email protected]. To be published in Reviews of Modern Physic
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