Entanglement sudden death and sudden birth in two uncoupled spins

We investigate the entanglement evolution of two qubits interacting with a common environment trough an Heisenberg XX mechanism. We reveal the possibility of realizing the phenomenon of entanglement sudden death as well as the entanglement sudden birth acting on the environment. Such analysis is of maximal interest at the light of the large applications that spin systems have in quantum information theory

A criterion for entanglement in two two-level systems

We prove a necessary and sufficient condition for the occurrence of entanglement in two two-level systems, simple enough to be of experimental interest. Our results are illustrated in the context of a spin star system analyzing the exact entanglement evolution of the central couple of spins.Comment: 4 pages, Submitted to Physical Review Letter

Teachers’ Perspectives on Year Two Implementation of a Kindergarten Readiness Assessment

In this study we examined teachers’ perspectives regarding the second year of implementing a Kindergarten Readiness Assessment (KRA). Using a mixed-methods approach, we focused on the administration process, the perceived benefits of the assessment, and how teachers used the assessment to inform instruction. We also investigated whether these differed by teacher and district characteristics and how KRA experiences were different in the second year of implementation. Research Findings: Teachers generally did not view the KRA as beneficial for instruction or for students, reporting administration difficulties, inadequate KRA content, and limited utility of KRA data for supporting instruction as ongoing barriers to KRA use. Although the administration process seemed to be easier in the second year, teachers still reported it as burdensome, cutting into important beginning of kindergarten activities. Notably, teacher training and experience were associated with perceptions. Practice or Policy: Reasons for perceived lack of utility have important implications for future KRA design and implementation. These include better integration of KRAs into existing assessment systems, recognizing the added burden of KRAs to teachers (particularly at the beginning of kindergarten), and the role that additional training may have in supporting use of KRAs at the local level

W-like states of N uncoupled spins 1/2

The exact dynamics of a disordered spin star system, describing a central spin coupled to N distinguishable and non interacting spins 1/2, is reported. Exploiting their interaction with the central single spin system, we present possible conditional schemes for the generation of W-like states, as well as of well-defined angular momentum states, of the N uncoupled spins. We provide in addition a way to estimate the coupling intensity between each of the N spins and the central one. Finally the feasibility of our procedure is briefly discussed.Comment: 8 pages, 2 figures, accepted for publication in European Physical Journal Special Topic

Human tularemia in Italy. Is it a re-emerging disease?

In order to evaluate whether tularemia is re-emerging in Italy, data on mortality and morbidity (obtained by the National Institute of Statistics; ISTAT), Italian cases described in the scientific literature and data concerning hospitalizations for tularemia (obtained by the National Hospital Discharge Database) were analysed. From 1979 to 2010, ISTAT reported 474 cases and no deaths. The overall number of cases obtained from the literature review was at least 31% higher than that reported by ISTAT. Moreover, the number of cases reported by ISTAT was 3·5 times smaller than hospitalized cases. The real frequency of the disease should be carefully investigated and taken into account in order to implement specific prevention measures.Tularemia is a contagious infectious disease due to Francisiella tularensis that can cause serious clinical manifestations and significant mortality if untreated. Although the frequency and significance of the disease has diminished over the last decades in Central Europe, over the past few years, there is new evidence suggesting that tularemia has re-emerged worldwide. To know the real epidemiology of the disease is at the root of correct control measures. In order to evaluate whether tularemia is re-emerging in Italy, data on mortality and morbidity (obtained by the National Institute of Statistics; ISTAT), Italian cases described in the scientific literature and data concerning hospitalizations for tularemia (obtained by the National Hospital Discharge Database) were analysed. From 1979 to 2010, ISTAT reported 474 cases and no deaths. The overall number of cases obtained from the literature review was at least 31% higher than that reported by ISTAT. Moreover, the number of cases reported by ISTAT was 3·5 times smaller than hospitalized cases. In Italy tularemia is sporadic, rarely endemic and self-limiting; but, although the trend of reported tularemia does not support the hypothesis of a re-emerging disease, the study demonstrates a wide underreporting of the disease. The real frequency of the disease should be carefully investigated and taken into account in order to implement specific prevention measures

Non-Markovian dissipative dynamics of two coupled qubits in independent reservoirs: a comparison between exact solutions and master equation approaches

The reduced dynamics of two interacting qubits coupled to two independent bosonic baths is investigated. The one-excitation dynamics is derived and compared with that based on the resolution of appropriate non-Markovian master equations. The Nakajima-Zwanzig and the time-convolutionless projection operator techniques are exploited to provide a description of the non-Markovian features of the dynamics of the two-qubits system. The validity of such approximate methods and their range of validity in correspondence to different choices of the parameters describing the system are brought to light.Comment: 6 pages, 3 figures. Submitted to PR

Matrix Structure Exploitation in Generalized Eigenproblems Arising in Density Functional Theory

In this short paper, the authors report a new computational approach in the context of Density Functional Theory (DFT). It is shown how it is possible to speed up the self-consistent cycle (iteration) characterizing one of the most well-known DFT implementations: FLAPW. Generating the Hamiltonian and overlap matrices and solving the associated generalized eigenproblems $Ax = \lambda Bx$ constitute the two most time-consuming fractions of each iteration. Two promising directions, implementing the new methodology, are presented that will ultimately improve the performance of the generalized eigensolver and save computational time.Comment: To appear in the proceedings of 8th International Conference on Numerical Analysis and Applied Mathematics (ICNAAM 2010

Hierarchies of primitive recursive wordsequence functions: Comparisons and decision problems

AbstractIn this paper we consider wordsequence functions, i.e., functions of the type ƒ: Σ∗′ → Σ∗‵ where Σ is a finite alphabet and r ⩾ 0, s > 0. By starting with finite sets of basic functions and by taking the closure with respect to composition, cylindrification and iteration, we give some characterizations of primitive recursive wordsequence functions. We define some hierarchies of length ω2 of these functions by bounding the number of successive compositions and the depth of the nested iterations in the definitions of the functions. In such a manner we obtain refinements of the Axt, Grzegorczyk and Meyer and Ritchie generalized hierarchies of length ω of primitive recursive wordfunctions defined by Von Henke, Indermark and Weihrauch (1972).We consider Loop programs on words (see Ausiello and Moscarini (1976)) by allowing more than one output register, and we prove that the class of functions computed by these programs coincides with the class of primitive recursive wordsequence functions. The hierarchies of functions induce some hierarchies of programs.For the case of functions ƒ: Σ∗′ → Σ∗, our hierarchies are compared with the Axt et al. generalized hierarchies.We also compare our hierarchies with storage hierarchies, and we analyze the power of the Loop programs as acceptors.Finally, we state some decidability results for the considered classes