Protecting the SWAP\sqrt{SWAP} operation from general and residual errors by continuous dynamical decoupling

We study the occurrence of errors in a continuously decoupled two-qubit state during a $\sqrt{SWAP}$ quantum operation under decoherence. We consider a realization of this quantum gate based on the Heisenberg exchange interaction, which alone suffices for achieving universal quantum computation. Furthermore, we introduce a continuous-dynamical-decoupling scheme that commutes with the Heisenberg Hamiltonian to protect it from the amplitude damping and dephasing errors caused by the system-environment interaction. We consider two error-protection settings. One protects the qubits from both amplitude damping and dephasing errors. The other features the amplitude damping as a residual error and protects the qubits from dephasing errors only. In both settings, we investigate the interaction of qubits with common and independent environments separately. We study how errors affect the entanglement and fidelity for different environmental spectral densities.Comment: Extended version of arXiv:1005.1666. To appear in PR

Relic Abundances and the Boltzmann Equation

I discuss the validity of the quantum Boltzmann equation for the calculation of WIMP relic densities.Comment: 5 pages, no figures; talk given at Dark Matter 2000; an important reference is added in the revised versio

A Model for Planning TELCO Work-Field Activities Enabled by Genetic and Ant Colony Algorithms

Telecommunication Company’s (TELCO) are continuously delivering their efforts on the effectiveness of their daily work. Planning the activities for their workers is a crucial sensitive, and time-consuming task usually taken by experts. This plan aims to find an optimized solution maximizing the number of activities assigned to workers and minimizing the inherent costs (e.g., labor from workers, fuel, and other transportation costs). This paper proposes a model that allows computing a maximized plan for the activities assigned to their workers, allowing to alleviate the burden of the existing experts, even if supported by software implementing rule-based heuristic models. The proposed model is inspired by nature and relies on two stages supported by Genetic and Ant Colony evolutionary algorithms. At the first stage, a Genetic Algorithms (GA) identifies the optimal set of activities to be assigned to workers as the way to maximize the revenues. At a second step, an Ant Colony algorithm searches for an efficient path among the activities to minimize the costs. The conducted experimental work validates the effectiveness of the proposed model in the optimization of the planning TELCO work-field activities in comparison to a rule-based heuristic model.info:eu-repo/semantics/publishedVersio

EDUCAÇÃO SEXUAL NA ESCOLA – CONTEXTOS PARA A MUDANÇA

A educação sexual é hoje uma das áreas de intervenção prioritária no nosso País e ocupa um lugar de interesse no âmbito das políticas educativas e de saúde pública na União Europeia. Diversos estudos têm sido desenvolvidos abordando a problemática da sexualidade na adolescência( 1,2,3,4), os quais constatam a precocidade do início das relações sexuais entre os adolescentes, a inexistência de um parceiro sexual regular e a reduzida utilização sistemática do preservativo nas situações de risco acrescido. Perante este panorama tornam-se relevantes as intervenções de educação sexual dirigidas aos indivíduos nesta fase da vida. Até porque é inquestionável o papel crucial que a sexualidade desempenha no crescimento e desenvolvimento do adolescente, no relacionamento interpessoal, no respeito, na comunicação, na autoestima, na assertividade e na autoconfiança. Face ao exposto optou-se pela metodologia de investigação ação. Na fase diagnóstica procedeu-se à aplicação de um conjunto de instrumentos dos quais destacamos o questionário: avaliação de atitudes dos professores face á Educação sexual (QAAPES)(5); conceções e práticas face à Educação sexual – versão para professores(6). Os resultados apresentados reportam-se apenas à primeira fase do processo. Os mesmos permitiram-nos constatar o reconhecimento da educação sexual na escola como uma necessidade explícita. Na opinião dos professores esta diz respeito a todos os professores e deve ser abordada preferencialmente na componente letiva. Para estes a principal finalidade da educação sexual é desenvolver as competências dos alunos para que consigam viver a sua sexualidade de uma forma mais saudável

Imaging 3D seismic velocity along the seismogenic zone of Algarve region (southern Portugal)

The present seismic tomographic study is focused around Algarve region, in South of Portugal. To locate the seismic events and find the local velocity structure of epicentral area, the P and S arrival times at 38 stations are used. The data used in this study were obtained during the Algarve campaign which worked from January/2006 to July/2007. The preliminary estimate of origin times and hypocentral coordinates are determined by the Hy- poinverse program. Linearized inversion procedure was applied to comprise the following two steps: 1) finding the minimum 1D velocity model using Velest and 2) simultaneous relocation of hypocenters and determination of local velocity structure. The velocity model we have reached is a 10 layer model which gave the lowest RMS, after several runnings of eight different velocity models that we used “a priori”. The model parameterization assumes a continuous velocity field between 4.5 km/s and 7.0 km/s until 30 km depth. The earth structure is represented in 3D by velocity at discrete points, and velocity at any intervening point is determined by linear interpolation among the surrounding eight grid points. A preliminary analysis of the resolution capabilities of the dataset, based on the Derivative Weight Sum (DWS) distribution, shows that the velocity structure is better resolved in the West part of the region between the surface to15 km. The resulting tomographic image has a prominent low-velocity anomaly that shows a maximum decrease in P-wave velocity in the first 12 kms in the studied region. We also identified the occurrence of local seismic events of reduced magnitude not catalogued, in the neighbourhood of Almodôvar (low Alentejo). The spatial distribution of epicentres defines a NE-SW direction that coincides with the strike of the mapped geological faults of the region and issued from photo-interpretation. Is still expectable to refine the seismicity of the region of Almodôvar and establish more rigorously its role in the seismotectonic picture of the region. This work is expected to produce a more detailed knowledge of the structure of the crust over the region of Algarve, being able to identify seismogenic zones, potentially generators of significant seismic events and also the identification of zones of active faults

Validation of the Lower Tagus Valley velocity and structural model using ambient noise broadband measurements

Along his history the Lower Tagus Valley (LTV) region was shaken by several earthquakes, some of them were produced in large ruptures of offshore structures located southwest of the Portuguese coastline, among these we the Lisbon earthquake of 1 November 1755; other moderates earthquakes were produced by local sources such as the 1344, 1531 and the 1909 Benavente earthquake. In order to promote an improved assessment of the seismic hazard in this region, we propose the introduction of realistic methods on the prediction of ground motion produced by moderate to large earthquakes in LTV. This process involves the establishment of a structural 3D model based on all the available geophysical and geotechnical data on the area (seismic, gravimetric, deep wells and geological outcrops) and the determination of wave propagation from a finite difference method: by applying the E3D program [1,2]. To confirm this model we use broadband ambient noise measurements collected in two profiles with azimuth perpendicular to the basin axis and we applied the horizontal to vertical (H/V) spectral ratio method [3] to the recordings in order to estimate the amplification of the basin. The H/V curves obtained reveals the existence of two low frequency peaks centered on 0.2 a 1 Hz frequencies[4]. These peaks are strongly related with the thickness of Cenozoic and alluvial sediments. By inversion of the H/V curve, we obtain a more detailed velocity model for the region where the profile were determined, which is in good agreement with borehole data and other results obtained with magnetic and seismic reflection methods

Localization on short-range potentials in dissipative quantum mechanics

In this Letter the problem of the existence of a state localized on a weak short-range attractive potential in the presence of dissipation is considered. It is shown that, contrary to the pure quantum case, a localized state is produced in any number of dimensions, while in low dimensions dissipation leads to much stronger localization. The results have physical implications for the dissipative dynamics of objects such as heavy particles in Fermi liquids and for superconductivity in high-$T_c$ materials.Comment: RevTeX, 4 pages, 1 figure. Published versio

Criatividade, autoconceito e rendimento escolar em alunos do ensino básico

Disponível em: Veiga, F. & Caldeira, M. (2006). Criatividade, autoconceito e rendimento escolar em alunos do ensino básico In Santos, N., Lima, M. L., Melo, M. M., Candeias, A., Grácio, M. L., & Calado, A. (orgs.). Livro de Actas do VI Simpósio Nacional de Investigação em Psicologia (pp. 77-97). Évora, Portugal. ISBN: 978-972-98136-9-6Com este estudo pretendeu-se estudar como se relacionam a criatividade, o autoconceito e o rendimento escolar em alunos do ensino básico. A amostra foi constituída por 350 alunos de do 6º e do 9º anos de escolaridade, de escolas da Grande Lisboa e do distrito de Faro, englobando sujeitos dos dois sexos e de diferentes nacionalidades. Para a avaliação do autoconceito académico recorreu-se ao Self-Concept as a Learner Scale, já adaptada para Portugal. A criatividade foi avaliada com o instrumento denominado Torrance Tests of Creative Thinking. A análise dos resultados permitiu observar, em variadas situações, diferenças significativas nas dimensões das atitudes dos alunos face a si mesmos em função da criatividade, com superiores resultados nos alunos vistos como criativos, verificando-se, ainda, correlações esperadas entre os valores da criatividade e do rendimento escolar. Os resultados foram interpretados numa perspectiva cognitivo-social e sugerem novas investigações acerca das dimensões da riatividade e de variáveis específicas, quer pessoais quer escolares

Improving the Knowledge on Seismogenic Sources in the Lower Tagus Valley for Seismic Hazard Purposes

The Lower Tagus Valley, that includes the metropolitan area of Lisbon, has been struck by several earthquakes which produced significant material damage and loss of lives. Their exact location remains unknown. Our goal is to shed some light into the seismogenic sources in the area using seismic reflection and geological data. In areas with no seismic coverage, potential-field data interpretation was carried out. Seismicity was overlaid to the potential seismogenic structures and high-resolution data was acquired in order to confirm which structures have been active into the Quaternary. Three major fault-zones affecting the Neogene were identified: V. F. Xira, Samora-Alcochete and Pinhal Novo. For the first fault, strong evidences suggest it is active. The other two fault-zones and other structures previously unknown can be correlated with several epicentres. Empirical relationships between maximum moment magnitude and fault area indicate that MW > 6.5 earthquakes can be expected for the larger structures