Dynamical Localization in Quasi-Periodic Driven Systems

We investigate how the time dependence of the Hamiltonian determines the occurrence of Dynamical Localization (DL) in driven quantum systems with two incommensurate frequencies. If both frequencies are associated to impulsive terms, DL is permanently destroyed. In this case, we show that the evolution is similar to a decoherent case. On the other hand, if both frequencies are associated to smooth driving functions, DL persists although on a time scale longer than in the periodic case. When the driving function consists of a series of pulses of duration $\sigma$, we show that the localization time increases as $\sigma^{-2}$ as the impulsive limit, $\sigma\to 0$, is approached. In the intermediate case, in which only one of the frequencies is associated to an impulsive term in the Hamiltonian, a transition from a localized to a delocalized dynamics takes place at a certain critical value of the strength parameter. We provide an estimate for this critical value, based on analytical considerations. We show how, in all cases, the frequency spectrum of the dynamical response can be used to understand the global features of the motion. All results are numerically checked.Comment: 7 pages, 5 figures included. In this version is that Subsection III.B and Appendix A on the quasiperiodic Fermi Accelerator has been replaced by a reference to published wor

Quantum walk on the line: entanglement and non-local initial conditions

The conditional shift in the evolution operator of a quantum walk generates entanglement between the coin and position degrees of freedom. This entanglement can be quantified by the von Neumann entropy of the reduced density operator (entropy of entanglement). In the long time limit, it converges to a well defined value which depends on the initial state. Exact expressions for the asymptotic (long-time) entanglement are obtained for (i) localized initial conditions and (ii) initial conditions in the position subspace spanned by the +1 and -1 position eigenstates.Comment: A few mistakes where corrected. One of them leads to a factor of 2 in eq. (49), the other results remain unchanged. In this version, several figures where replaced by color version

Quantum random walk on the line as a markovian process

We analyze in detail the discrete--time quantum walk on the line by separating the quantum evolution equation into Markovian and interference terms. As a result of this separation, it is possible to show analytically that the quadratic increase in the variance of the quantum walker's position with time is a direct consequence of the coherence of the quantum evolution. If the evolution is decoherent, as in the classical case, the variance is shown to increase linearly with time, as expected. Furthermore we show that this system has an evolution operator analogous to that of a resonant quantum kicked rotor. As this rotator may be described through a quantum computational algorithm, one may employ this algorithm to describe the time evolution of the quantum walker.Comment: few typos corrected, 13 pages, 2 figures, to appear in Physica

Counsellor's role and function as perceived by students, teachers and educational councellors at credit course secondary schools in Kuwait

This study investigates the perceptions of teachers, students and educational counsellors regarding the role and function of educational counsellors in credit course secondary schools in Kuwait. A field study was carried out in ten credit course secondary schools located across Kuwait's five educational geographical zones. A sample of 300 students, 300 teachers and 30 educational counsellors completed a twenty-item questionnaire, the data from which were analysed using the SPSS statistical package. Differences in perceptions were found between the three groups, suggesting role conflict and ambiguity.To obtain information about the actual role of educational counsellors, all 32 educational counsellors from all the credit course secondary schools in Kuwait were interviewed, and were asked to complete a checklist, and answer a time-scale questionnaire. The results confirmed the view that role conflict and ambiguity are impairing the performance and lowering the morale of educational counsellors. Possible causes of the conflict are identified, and recommendations made for modification of the guidance and counselling programmes

Markovian Behaviour and Constrained Maximization of the Entropy in Chaotic Quantum Systems

The separation of the Schr\"{o}dinger equation into a Markovian and an interference term provides a new insight in the quantum dynamics of classically chaotic systems. The competition between these two terms determines the localized or diffusive character of the dynamics. In the case of the Kicked Rotor, we show how the constrained maximization of the entropy implies exponential localization.Comment: 8 pages, 2 figure

Effects of non-local initial conditions in the Quantum Walk on the line

We report an enhancement of the decay rate of the survival probability when non-local initial conditions in position space are considered in the Quantum Walk on the line. It is shown how this interference effect can be understood analytically by using previously derived results. Within a restricted position subspace, the enhanced decay is correlated with a maximum asymptotic entanglement level while the normal decay rate corresponds to initial relative phases associated to a minimum entanglement level.Comment: 5 pages, 1 figure, Elsevier style, to appear in Physica

El efecto socializador del medio televisivo en jóvenes. Influencia de las conductas de gestión del conflicto mostradas por personajes de series de ficción

Clearly the influence of television in society, being the study of violence and its impact on children and young people the subject of most investigations. How to manage conflict becomes a variable indicative of violent behavior, therefore, this work has been an analysis of the styles of managing conflicts of characters in the television series most viewed by young people, being results based on the sex of the characters analyzed, and associating these different styles of behaviors and attitudes that young men and women assigned to.Resulta evidente la influencia del medio televisivo en la sociedad, siendo el estudio de la violencia y sus consecuencias en niños y jóvenes el objeto de la mayoría de las investigaciones al respecto. El modo de gestionar los conflictos se convierte en una variable indicativa de conductas violentas, por ello, este trabajo ha realizado un análisis de los estilos de gestionar conflictos de personajes de las series televisivas más vistas por jóvenes, hallándose resultados en función del sexo de los personajes analizados, y asociándose estas diferencias de estilos a conductas y actitudes que los jóvenes asignan a hombres o mujeres

The Health-e-Waterways Project: Data Integration for Smarter Collaborative Whole-of-Water Cycle Management

The Health-e-Waterways Project is a collaboration between the University of Queensland, Microsoft Research and the South East Queensland Healthy Waterways Partnership (SEQ-HWP) (a consortium of over 60 local government, state agency, universities, community and environmental organizations). The aim of the project is to develop a highly innovative framework and set of services to enable streamlined access to a collection of real-time, near-real-time and static datasets acquired through ecosystem health monitoring programs (EHMP) in South East Queensland. This paper describes the underlying water information management system and Web Portal that we are developing to enable the sharing and integration of the high quality data and models for SEQ water resource managers. In addition we will describe the interactive and dynamic ecosystem reporting services that we have developed and the WaterWiki that is being established to enable knowledge exchange between the online community of Queensland’s water stakeholders