Satisfying the Einstein-Podolsky-Rosen criterion with massive particles

In 1935, Einstein, Podolsky and Rosen (EPR) questioned the completeness of quantum mechanics by devising a quantum state of two massive particles with maximally correlated space and momentum coordinates. The EPR criterion qualifies such continuous-variable entangled states, where a measurement of one subsystem seemingly allows for a prediction of the second subsystem beyond the Heisenberg uncertainty relation. Up to now, continuous-variable EPR correlations have only been created with photons, while the demonstration of such strongly correlated states with massive particles is still outstanding. Here we report on the creation of an EPR-correlated two-mode squeezed state in an ultracold atomic ensemble. The state shows an EPR entanglement parameter of 0.18(3), which is 2.4 s.d. below the threshold 1/4 of the EPR criterion. We also present a full tomographic reconstruction of the underlying many-particle quantum state. The state presents a resource for tests of quantum nonlocality and a wide variety of applications in the field of continuous-variable quantum information and metrology.

EVALUACIÓN DEL ÁREA DE CIENCIAS APLICADAS (600 DEWEY) DE LA COLECCIÓN DE LA BIBLIOTECA “JOAQUIN GARCÍA MONGE”

Con esta investigación se pretende determinar la calidad, actualidad, grado de satisfacción de los usuarios, uso y pertinencia de la colección del área de Ciencias Aplicadas de la Biblioteca “Joaquín García Monge” en relación con las necesidades de los usuarios.Se seleccionó como estudio de caso la colección del área de Ciencias Aplicadas de la Biblioteca “Joaquín García Monge” que cubre ciencias ambientales, agrarias y forestales; física y química industrial; medicina veterinaria, psiquiatría, administración, contabilidad, mercadeo, manualidades y mecanografía. Se evaluará el fondo bibliográfico correspondiente únicamente a los libros de la colección y material bibliográfico de referencia.

Metoda projektów w uczeniu się i nauczaniu fizyki w gimnazjum

Wydział Studiów Edukacyjnych: Zakład Pedeutologii

A modelação matemática com recurso a tecnologia: Um estudo em contexto de colaboração entre professoras de matemática e de física-química

Este estudo teve como objectivo compreender o desenvolvimento de tarefas de modelação, por parte de uma professora de Matemática e de uma professora de Física­ Química, no âmbito de trabalho colaborativo. Para tal foram formuladas três questões orientadoras: 1. Como é que os professores seleccionam e preparam as tarefas de modelação a colocar aos alunos em situação de sala de aula? Que características das tarefas de modelação se mostram fundamentais para a sua selecção? 2. como desenvolvem os professores as tarefas de modelação na sala de aula? Como gerem e dinamizam as aulas onde colocam tarefas de modelação aos alunos? Que papel reservam ao professor e ao aluno? 3. como exploram os professores as potencialidades das calculadoras gráficas no desenvolvimento das tarefas de modelação? Que questões se colocam à utilização de sensores? O estudo decorreu numa escola secundária, durante o ano lectivo de 2005/06, sob proposta e com a participação da investigadora, envolvendo uma professora de Matemática e uma professora de Física-Química de uma mesma turma de 100 ano. O grupo colaborativo reuniu regularmente e preparou e leccionou aulas com tarefas de modelação matemática, recorrendo a calculadoras gráficas e sensores, tarefas e tecnologias novas para ambas as professoras. A metodologia utilizada na investigação tem natureza qualitativa, tendo sido realizadas duas entrevistas longas a cada professora, uma no início e outra no fim do estudo, bem como entrevistas de curta duração às professoras após cada uma das aulas onde foram desenvolvidas as tarefas. Foram também recolhidos registos das sessões colectivas de trabalho e elaborado um "diário de bordo". O estudo permitiu formular as seguintes conclusões: - Quando as professoras seleccionavam as tarefas de modelação a propor aos seus alunos tinham em consideração o cumprimento dos programas, os conteúdos a abordar e a diversidade de questões que se podem formular sobre os mesmos e o interesse e significado da experiência para os alunos. - O tempo que é necessário para a preparação e execução das tarefas de modelação pareceu ser factor de grande peso na sua selecção. - O elevado número de alunos por turma pode ser factor um negativo para o desenvolvimento de tarefas de modelação na sala de aula. -Na opinião das professoras, o recurso à calculadora gráfica e aos sensores para realizar a recolha de dados relativos a uma tarefa de modelação tomou-as mais apelativas e ajudou os alunos a compreender a situação em causa assim como permitiu tomar mais nítida a relação entre a Matemática e a Física. ABSTRACT: This study aimed to understand the development of modelling tasks, by a Mathematics teacher and a Physics-Chemistry teacher, as part of collaborative work. For this study were formulated three guidelines: 1. How do teachers select and prepare the modelling tasks to present to the students in a classroom situation? What characteristics of these tasks are essential for their selection? 2. How do teachers develop the modelling tasks in the classroom? How do they manage and dynamize the classes where the modelling tasks took place? What role it's reserd to the teacher and the student? 3. How do teachers exploit the potential of graphics calculator in the development of the modelling tasks? What issues arise for the use of sensors? This study took place at a secundary school during the academic year 2005/06, as a suggestion and with the participation of the researcher, involving a Mathematics teacher and a Physics-Chemistry teacher of the same class (10th grade). The collaborative group had regular meetings and prepared and developed modellin tasks in the classroom using graphics calculator and sensors, which was a new activity for all the teachears. The methodology used has a qualitative nature. Two interviews were made to each teacher, one at baseline and another at the end of the study, fourteen work sections and three modelling tasks were explored in classroom context after which followed small interviews to the teacher that gave the class. ln addition records were also made in a small "log-book". This study allowed to reach the following conclusions: - When the teachers select the modelling tasks to offer its students they take into account the programs, the contents and the diversity of questions that can be made on it and the interest and significance of the experience for students. - The time needed for preparation and implementation of the modelling tasks is another factor of great weight in its selection. - The high number of student per class can be a negative factor for the development of modelling tasks in the classroom. Iii - ln the teacher’s opinion, the use of the graphics calculator and sensors to collect data on a modelling tasks makes its more attractive and helps students to understand the situation and makes clearer the link between Mathematics and Physics.

Experimental study of the turbulent field behind a perforated vortex generator

International audience

Shaken not stirred: creating exotic angular momentum states by shaking an optical lattice

We propose a method to create higher orbital states of ultracold atoms in the Mott regime of an optical lattice. This is done by periodically modulating the position of the trap minima (known as shaking) and controlling the interference term of the lasers creating the lattice. These methods are combined with techniques of shortcuts to adiabaticity. As an example of this, we show specifically how to create an anti-ferromagnetic type ordering of angular momentum states of atoms. The specific pulse sequences are designed using Lewis-Riesenfeld invariants and a fourlevel model for each well. The results are compared with numerical simulations of the full Schrodinger equation.

Cálculo de constantes ópticas de películas delgadas de Cu3BiS3 a través del método de Wolfe

Se calculó la obtención de las constantes ópticas usando el método de Wolfe. Dichas contantes: coeficiente de absorción (α), índice de refracción (n) y espesor de una película delgada (d ), son de importancia en el proceso de caracterización óptica del material. Se realizó una comparación del método del Wolfe con el método empleado por R. Swanepoel. Se desarrolló un modelo de programación no lineal con restricciones, de manera que fue posible estimar las constantes ópticas de películas delgadas semiconductoras, a partir únicamente, de datos de transmisión conocidos. Se presentó una solución al modelo de programación no lineal para programación cuadrática. Se demostró la confiabilidad del método propuesto, obteniendo valores de α = 10378.34 cm−1, n = 2.4595, d =989.71 nm y Eg = 1.39 Ev, a través de experimentos numéricos con datos de medidas de transmitancia espectral en películas delgadas de Cu3BiS3.

Non-standard signatures from Cosmic Microwave Background polarisation

In this Thesis we focus on non-standard signatures from CMB polarisation, which might hint at the existence of new phenomena beyond the standard models for Cosmology and Particle physics. With the Planck ESA mission, CMB temperature anisotropies have been observed at the cosmic variance limit, but polarisation remains to be further investigated. CMB polarisation data are important not only because they contribute to provide tighter constraints of cosmological parameters but also because they allow the investigation of physical processes that would be precluded if just the CMB temperature maps were considered. We take polarisation data into account to assess the statistical significance of the anomalies currently observed only in the CMB temperature map and to constrain the Cosmic Birefringence (CB) effect, which is expected in parity-violating extensions of the standard electromagnetism. In particular, we propose a new one-dimensional estimator for the lack of power anomaly capable of taking both temperature and polarisation into account jointly. With the aim of studying the anisotropic CB we develop and perform two different and complementary methods able to evaluate the power spectrum of the CB. Finally, by employing these estimators and methodologies on Planck data we provide new constraints beyond what already known in literature. The measure of CMB polarisation represents a technological challenge and to make accurate estimates, one has to keep an exquisite control of the systematic effects. In order to investigate the impact of spurious signal in forthcoming CMB polarisation experiments, we study the interplay between half-wave plates (HWP) non-idealities and the beams. Our analysis suggests that certain HWP configurations, depending on the complexity of Galactic foregrounds and the beam models, significantly impacts the B-mode reconstruction fidelity and could limit the capabilities of next-generation CMB experiments. We provide also a first study of the impact of non-ideal HWPs on CB.

Predicting magnetospheric dynamics with a coupled sun-to-Earth model: challenges and first results

Results from the first Sun-to-Earth coupled numerical model developed at the Center for Integrated Space Weather Modeling are presented. The model simulates physical processes occurring in space spanning from the corona of the Sun to the Earth's ionosphere, and it represents the first step toward creating a physics-based numerical tool for predicting space weather conditions in the near-Earth environment. Two 6- to 7-d intervals, representing different heliospheric conditions in terms of the three-dimensional configuration of the heliospheric current sheet, are chosen for simulations. These conditions lead to drastically different responses of the simulated magnetosphere-ionosphere system, emphasizing, on the one hand, challenges one encounters in building such forecasting tools, and on the other hand, emphasizing successes that can already be achieved even at this initial stage of Sun-to-Earth modeling.

High-latitude particle precipitation and its relationship to magnetospheric source regions

Two central issues in magnetospheric research are understanding the mapping of the low-altitude ionosphere to the distant regions of the magnetsphere, and understanding the relationship between the small-scale features detected in the various regions of the ionosphere and the global properties of the magnetosphere. The high-latitude ionosphere, through its magnetic connection to the outer magnetosphere, provides an important view of magnetospheric boundaries and the physical processes occurring there. All physical manifestations of this magnetic connectivity (waves, particle precipitation, etc.), however, have non-zero propagation times during which they are convected by the large-scale magnetospheric electric field, with phenomena undergoing different convection distances depending on their propagation times. Identification of the ionospheric signatures of magnetospheric regions and phenomena, therefore, can be difficult. Considerable progress has recently been made in identifying these convection signatures in data from low- and high-altitude satellites. This work has allowed us to learn much about issues such as: the rates of magnetic reconnection, both at the dayside magnetopause and in the magnetotail; particle transport across the open magnetopause; and particle acceleration at the magnetopause and the magnetotail current sheets.

Ionospheric origin of magnetospheric O+ ions

Flows of thermal atomic oxygen (O+) ions are deduced from topside ionospheric plasma density profiles. The mean flux within most of the polar cap is of the order of 10^12 m^{−2} s^{−1}, a figure which is consistent with both theoretical and experimental estimates of the light ion polar wind at greater altitudes. Larger flows (up to 6 × 10^12 m^{−2} s^{−1}) are observed near the poleward edge of the night-side statistical auroral oval, a feature not reproduced in the light ion flux. The implication is one of a low altitude acceleration mechanism, acting upon the O+ ions at these latitudes and at heights above that at which the fluxes are observed. Such a process would enable ions to escape from the ionosphere because they do not exchange charge with neutral hydrogen. The observations are in general agreement with energetic O+ ions as previously observed in various parts of the magnetosphere.

3D Ionospheric Effects on HF Propagation and Heating

The thesis uses a three-dimensional, first-principles model of the ionosphere in combination with High Frequency (HF) raytracing model to address key topics related to the physics of HF propagation and artificial ionospheric heating. In particular: 1. Explores the effect of the ubiquitous electron density gradients caused by Medium Scale Traveling Ionospheric Disturbances (MSTIDs) on high-angle of incidence HF radio wave propagation. Previous studies neglected the all-important presence of horizontal gradients in both the cross- and down-range directions, which refract the HF waves, significantly changing their path through the ionosphere. The physics-based ionosphere model SAMI3/ESF is used to generate a self-consistently evolving MSTID that allows for the examination of the spatio-temporal progression of the HF radio waves in the ionosphere. 2. Tests the potential and determines engineering requirements for ground- based high power HF heaters to trigger and control the evolution of Equatorial Spread F (ESF). Interference from ESF on radio wave propagation through the ionosphere remains a critical issue on HF systems reliability. Artificial HF heating has been shown to create plasma density cavities in the ionosphere similar to those that may trigger ESF bubbles. The work explores whether HF heating may trigger or control ESF bubbles. 3. Uses the combined ionosphere and HF raytracing models to create the first self-consistent HF Heating model. This model is utilized to simulate results from an Arecibo experiment and to provide understanding of the physical mechanism behind observed phenomena. The insights gained provide engineering guidance for new artificial heaters that are being built for use in low to middle latitude regions. In accomplishing the above topics: (i) I generated a model MSTID using the SAMI3/ESF code, and used a raytrace model to examine the effects of the MSTID gradients on radio wave propagation observables; (ii) I implemented a three- dimensional HF heating model in SAMI3/ESF and used the model to determine whether HF heating could artificially generate an ESF bubble; (iii) I created the first self-consistent model for artificial HF heating using the SAMI3/ESF ionosphere model and the MoJo raytrace model and ran a series of simulations that successfully modeled the results of early artificial heating experiments at Arecibo.

Ionospheric Turbulence Near the Upper Hybrid Layer: Theory and Experiment

The thesis presents experimental results, simulations, and theory on turbulence excited in magnetized plasmas near the ionosphere’s upper hybrid layer. The results include: The first experimental observations of super small striations (SSS) excited by the High-Frequency Auroral Research Project (HAARP) The first detection of high-frequency (HF) waves from the HAARP transmitter over a distance of 16x10^3 km The first simulations indicating that upper hybrid (UH) turbulence excites electron Bernstein waves associated with all nearby gyroharmonics Simulation results that indicate that the resulting bulk electron heating near the upper hybrid (UH) resonance is caused primarily by electron Bernstein waves parametrically excited near the first gyroharmonic. On the experimental side we present two sets of experiments performed at the HAARP heating facility in Alaska. In the first set of experiments, we present the first detection of super-small (cm scale) striations (SSS) at the HAARP facility. We detected density structures smaller than 30 cm for the first time through a combination of satellite and ground based measurements. In the second set of experiments, we present the results of a novel diagnostic implemented by the Ukrainian Antarctic Station (UAS) in Verdansky. The technique allowed the detection of the HAARP signal at a distance of nearly 16 Mm, and established that the HAARP signal was injected into the ionospheric waveguide by direct scattering off of dekameter-scale density structures induced by the heater. On the theoretical side, we present results of Vlasov simulations near the upper hybrid layer. These results are consistent with the bulk heating required by previous work on the theory of the formation of descending artificial ionospheric layers (DIALs), and with the new observations of DIALs at HAARP’s upgraded effective radiated power (ERP). The simulations that frequency sweeps, and demonstrate that the heating changes from a bulk heating between gyroharmonics, to a tail acceleration as the pump frequency is swept through the fourth gyroharmonic. These simulations are in good agreement with experiments. We also incorporate test particle simulations that isolate the effects of specific wave modes on heating, and we find important contributions from both electron Bernstein waves and upper hybrid waves, the former of which have not yet been detected by experiments, and have not been previously explored as a driver of heating. In presenting these results, we analyzed data from HAARP diagnostics and assisted in planning the second round of experiments. We integrated the data into a picture of experiments that demonstrated the detection of SSS, hysteresis effects in simulated electromagnetic emission (SEE) features, and the direct scattering of the HF pump into the ionospheric waveguide. We performed simulations and analyzed simulation data to build the understanding of collisionless heating near the upper hybrid layer, and we used these simulations to show that bulk electron heating at the upper hybrid layer is possible, which is required by current theories of DAIL formation. We wrote a test particle simulation to isolate the effects of electron Bernstein waves and upper hybrid layers on collisionless heating, and integrated this code to work with both the output of Vlasov simulations and the input for simulations of DAIL formation.

Effect of ray and speed perturbations on ionospheric tomography by over-the-horizon radar: A new method

International audience

Reverse engineering in many-body quantum physics: Correspondence between many-body systems and effective single-particle equations

The mapping, exact or approximate, of a many-body problem onto an effective single-body problem is one of the most widely used conceptual and computational tools of physics. Here, we propose and investigate the inverse map of effective approximate single-particle equations onto the corresponding many-particle system. This approach allows us to understand which interacting system a given single-particle approximation is actually describing, and how far this is from the original physical many-body system. We illustrate the resulting reverse engineering process by means of the Kohn-Sham equations of density-functional theory. In this application, our procedure sheds light on the nonlocality of the density-potential mapping of density-functional theory, and on the self-interaction error inherent in approximate density functionals.