6,480 research outputs found
Open Quantum Systems. An Introduction
We revise fundamental concepts in the dynamics of open quantum systems in the
light of modern developments in the field. Our aim is to present a unified
approach to the quantum evolution of open systems that incorporates the
concepts and methods traditionally employed by different communities. We
present in some detail the mathematical structure and the general properties of
the dynamical maps underlying open system dynamics. We also discuss the
microscopic derivation of dynamical equations, including both Markovian and
non-Markovian evolutions.Comment: 100 pages, 3 figures. Updated version with typos corrected. Preprint
version of the published boo
Quantum Non-Markovianity: Characterization, Quantification and Detection
We present a comprehensive and up to date review on the concept of quantum
non-Markovianity, a central theme in the theory of open quantum systems. We
introduce the concept of quantum Markovian process as a generalization of the
classical definition of Markovianity via the so-called divisibility property
and relate this notion to the intuitive idea that links non-Markovianity with
the persistence of memory effects. A detailed comparison with other definitions
presented in the literature is provided. We then discuss several existing
proposals to quantify the degree of non-Markovianity of quantum dynamics and to
witness non-Markovian behavior, the latter providing sufficient conditions to
detect deviations from strict Markovianity. Finally, we conclude by enumerating
some timely open problems in the field and provide an outlook on possible
research directions.Comment: Review article. Close to published versio
OTOC, complexity and entropy in bi-partite systems
There is a remarkable interest in the study of Out-of-time ordered
correlators (OTOCs) that goes from many body theory and high energy physics to
quantum chaos. In this latter case there is a special focus on the comparison
with the traditional measures of quantum complexity such as the spectral
statistics, for example. The exponential growth has been verified for many
paradigmatic maps and systems. But less is known for multi-partite cases. On
the other hand the recently introduced Wigner separability entropy (WSE) and
its classical counterpart (CSE) provide with a complexity measure that treats
equally quantum and classical distributions in phase space. We have compared
the behavior of these measures in a system consisting of two coupled and
perturbed cat maps with different dynamics: double hyperbolic (HH), double
elliptic (EE) and mixed (HE). In all cases, we have found that the OTOCs and
the WSE have essentially the same behavior, providing with a complete
characterization in generic bi-partite systems and at the same time revealing
them as very good measures of quantum complexity for phase space distributions.
Moreover, we establish a relation between both quantities by means of a
recently proven theorem linking the second Renyi entropy and OTOCs.Comment: 6 pages, 5 figure
Classical to quantum correspondence in dissipative directed transport
We compare the quantum and classical properties of the (Quantum) Isoperiodic
Stable Structures -- (Q)ISSs -- which organize the parameter space of a
paradigmatic dissipative ratchet model, i.e. the dissipative modified kicked
rotator. We study the spectral behavior of the corresponding classical
Perron-Frobenius operators with thermal noise and the quantum superoperators
without it for small values. We find a remarkable similarity
between the classical and quantum spectra. This finding significantly extends
previous results -- obtained for the mean currents and asymptotic distributions
only -- and on the other hand unveils a classical to quantum correspondence
mechanism where the classical noise is qualitatively different from the quantum
one. This is crucial not only for simple attractors but also for chaotic ones,
where just analyzing the asymptotic distribution reveals insufficient.
Moreover, we provide with a detailed characterization of relevant eigenvectors
by means of the corresponding Weyl-Wigner distributions, in order to better
identify similarities and differences. Finally, this model being generic, it
allows us to conjecture that this classical to quantum correspondence mechanism
is a universal feature of dissipative systems.Comment: 7 pages, 6 figure
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Training Graduate Students in Utilization of Analytical Instruments in a Failure Analysis Course
Department of Engineering Technology at University of North Texas offers a graduate course on failure analysis (MSET 5150) during spring semesters. Partial requirement for the course is for students to submit a term paper based on their collected data related to a term project. Case studies are given to groups of students to work on actual failed components received from area industries. Results of their findings are presented at the end of the semester in both oral presentation form and written term paper form followed the format of a well-established technical papers. Results of such exercises allows graduate students devote skills in using scientific instruments and practice manuscript preparations for publication. This paper presents examples of a case studies done by groups of students who worked on failure analysis of components failed in an oil and gas industry. Students developed skills in utilization of scanning electron microscope (SEM), Energy Dispersive Spectroscopy (EDS), and Fourier Transform Infrared Spectrophotometry. This exercise has proven highly effective in introducing young engineers to real world problems in oil and gas industry and help them develop skills needed in performing failure analysis and steps involved.Cockrell School of Engineerin
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