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Depondt P.,University Pierre and Marie Curie | Levy J.-C.S.,CNRS Materials and Quantum Phenomena Laboratory
Physics Letters, Section A: General, Atomic and Solid State Physics

Vortex precession was simulated in two-dimensional magnetic dots. The Landau-Lifshitz equation with exchange and dipolar interactions was integrated at a low temperature with initial conditions consisting in a single vortex situated aside from the central position. This vortex precesses around the center of the sample and either can be expelled or converges towards the center. These relaxation processes are systematically studied. A simple qualitative explanation of the observed behaviors is proposed, including seemingly somewhat erratic ones. Intrinsic pinning of the vortex motion, unconnected with defects, is also observed and an explanation thereof provided. © 2011 Elsevier B.V. All rights reserved. Source

Ilisca E.,CNRS Materials and Quantum Phenomena Laboratory

Non-magnetic insulating catalysts are shown to be able to convert non-equilibrium mixtures of hydrogen by an electric mechanism. The molecular electrons feel the difference of temperature between the nuclei and the thermal bath, through their "Fermi" contact interaction, and consequently transfer the rotational angular momenta to the catalyst. This transfer, realized by the electrostatic interactions between the molecular and surface ionic electron clouds, is measured by non-diagonal exchange integrals. Our simple model of single-electron excitations interprets the experimental conversion rates recently observed on different surfaces (MOF or ASW) with different technics (infrared or ionization spectroscopy) and allows the study of the conversion rates in different contexts: thermal as well as transient, metallic or oxygen-induced, ion-molecule and molecule-molecule electron exchanges. © Copyright EPLA, 2013. Source

Sangouard N.,University of Geneva | Sangouard N.,CNRS Materials and Quantum Phenomena Laboratory | Simon C.,University of Geneva | Simon C.,University of Calgary | And 4 more authors.
Reviews of Modern Physics

The distribution of quantum states over long distances is limited by photon loss. Straightforward amplification as in classical telecommunications is not an option in quantum communication because of the no-cloning theorem. This problem could be overcome by implementing quantum repeater protocols, which create long-distance entanglement from shorter-distance entanglement via entanglement swapping. Such protocols require the capacity to create entanglement in a heralded fashion, to store it in quantum memories, and to swap it. One attractive general strategy for realizing quantum repeaters is based on the use of atomic ensembles as quantum memories, in combination with linear optical techniques and photon counting to perform all required operations. Here the theoretical and experimental status quo of this very active field are reviewed. The potentials of different approaches are compared quantitatively, with a focus on the most immediate goal of outperforming the direct transmission of photons. © 2011 American Physical Society. Source

Bringuier E.,CNRS Materials and Quantum Phenomena Laboratory | Bringuier E.,University Pierre and Marie Curie
Philosophical Magazine

In a liquid suspension, thermophoresis is the motion of a suspended particle under a temperature gradient. In a liquid binary mixture, thermodiffusion is the generation of a composition gradient upon application of a temperature gradient. A quantitative connection is established between the two phenomena without making assumptions about their mechanisms. It is shown that Galilean invariance and the choice of a Galilean reference frame play a key role in that connection. The results are not restricted to very dilute suspensions or mixtures. © 2011 Taylor & Francis. Source

Saad S.,CNRS Materials and Quantum Phenomena Laboratory | Hassine L.,University of Carthage | Elfahem W.,Regio IT Gesellschaft Mit Beschrankter Haftung
Photonic Sensors

The high efficiency hydrogen fiber Bragg grating (FBG) sensor is presented. The sensitive film was a new alliance of palladium-silver (Pd-Ag). In addition, the titanium (Ti) layer was used as the adhesive layer. The presented sensor showed the resolution of more than 60 pm/1% H2, and a fast response time of 4 s-5 s was guaranteed in the 0.1% H2-4% H2 range. Moreover, the life time of the sensor was investigated. The obtained results showed that the sensor had an enhanced life time. Furthermore, the sensor was applied in the propulsion system fuel tank model of the aerospace vehicle. The obtained results indicated that it is a prevention system against the disaster aerospace due to hydrogen leakage. © 2014 The Author(s). Source

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