365 research outputs found
Caractérisation des modes de coordination interpersonnelle au sein d'une équipe de basket-ball
Characterization of interpersonal coordination modes within a basket-ball team. The aim of our study was to analyze the construction of a collective activity. We focused on interpersonal coordination process within a basket-ball team during a match. We characterized the way how basketball players took mutually into account their respective activities. In order to consider in the same time both units of analysis, the individual one and the collective one, this study referred to the framework of the course of action theory (Theureau, 2006). Results allowed us to specify the relational network between players, the various coordination modes between two players and the different forms of team coordination. These results are discussed with regard to the nature of interactions within the team, and with regard to the notion of a collective action plan : they highlighted that some collective activity construction modalities are based on local overlapping coordination. These results thus question the status of a collective plan (as a scheme shared by all the players).Caractérisation de modes de coordination interpersonnels dans une équipe de basket-ball. Le but de notre étude était d'analyser la construction d'une activité collective. Nous nous sommes concentrés sur le processus de coordination interpersonnel dans une équipe de basket-ball pendant un match(une allumette). Nous avons caractérisé la voie comment les basketteurs ont pris mutuellement en considération leurs activités respectives. Pour considérer dans le même temps les deux unités d'analyse, le individuel et le collectif, cette étude a mentionné la structure du cours de théorie d'action (Theureau, 2006). Les résultats nous ont permis de spécifier le réseau relationnel entre des acteurs(joueurs), les modes de coordination divers entre deux acteurs(joueurs) et les formes(formulaires) différentes de coordination d'équipe. Ces résultats sont discutés en ce qui concerne la nature d'interactions dans l'équipe et en ce qui concerne la notion d'un plan d'action collectif : ils ont mis en évidence(ont surligné) ces quelques modalités de construction d'activité collectives sont basé sur la coordination de chevauchement locale. Ces résultats mettent ainsi en doute le statut d'un plan collectif (comme un plan(arrangement) partagé par tous les acteurs(joueurs))
Twin polaritons in semiconductor microcavities
The quantum correlations between the beams generated by polariton pair
scattering in a semiconductor microcavity above the parametric oscillation
threshold are computed analytically. The influence of various parameters like
the cavity-exciton detuning, the intensity mismatch between the signal and
idler beams and the amount of spurious noise is analyzed. We show that very
strong quantum correlations between the signal and idler polaritons can be
achieved. The quantum effects on the outgoing light fields are strongly reduced
due to the large mismatch in the coupling of the signal and idler polaritons to
the external photons
Correlated Photon Emission from a Single II-VI Quantum Dot
We report correlation and cross-correlation measurements of photons emitted
under continuous wave excitation by a single II-VI quantum dot (QD) grown by
molecular-beam epitaxy. A standard technique of microphotoluminescence combined
with an ultrafast photon correlation set-up allowed us to see an antibunching
effect on photons emitted by excitons recombining in a single CdTe/ZnTe QD, as
well as cross-correlation within the biexciton ()-exciton ()
radiative cascade from the same dot. Fast microchannel plate photomultipliers
and a time-correlated single photon module gave us an overall temporal
resolution of 140 ps better than the typical exciton lifetime in II-VI QDs of
about 250ps.Comment: 4 pages, 3 figures, to appear in Appl. Phys. Let
Quantum Non-demolition Measurements on Qubits
We discuss the characterization and properties of quantum non-demolition
(QND) measurements on qubit systems. We introduce figures of merit which can be
applied to systems of any Hilbert space dimension thus providing universal
criteria for characterizing QND measurements. We discuss the controlled-NOT
gate and an optical implementation as examples of QND devices for qubits. We
also discuss the QND measurement of weak values
Conditional preparation of a quantum state in the continuous variable regime: generation of a sub-Poissonian state from twin beams
We report the first experimental demonstration of conditional preparation of
a non classical state of light in the continuous variable regime. Starting from
a non degenerate OPO which generates above threshold quantum intensity
correlated signal and idler "twin beams", we keep the recorded values of the
signal intensity only when the idler falls inside a band of values narrower
than its standard deviation. By this very simple technique, we generate a
sub-Poissonian state 4.4dB below shot noise from twin beams exhibiting 7.5dB of
noise reduction in the intensity difference.Comment: 4 pages, Accepted in Phys. Rev. Let
Universal optimal broadband photon cloning and entanglement creation in one dimensional atoms
We study an initially inverted three-level atom in the lambda configuration
embedded in a waveguide, interacting with a propagating single-photon pulse.
Depending on the temporal shape of the pulse, the system behaves either as an
optimal universal cloning machine, or as a highly efficient deterministic
source of maximally entangled photon pairs. This quantum transistor operates
over a wide range of frequencies, and can be implemented with today's
solid-state technologies.Comment: 5 pages, 3 figure
Controlling the dynamics of a coupled atom-cavity system by pure dephasing : basics and potential applications in nanophotonics
The influence of pure dephasing on the dynamics of the coupling between a
two-level atom and a cavity mode is systematically addressed. We have derived
an effective atom-cavity coupling rate that is shown to be a key parameter in
the physics of the problem, allowing to generalize the known expression for the
Purcell factor to the case of broad emitters, and to define strategies to
optimize the performances of broad emitters-based single photon sources.
Moreover, pure dephasing is shown to be able to restore lasing in presence of
detuning, a further demonstration that decoherence can be seen as a fundamental
resource in solid-state cavity quantum electrodynamics, offering appealing
perspectives in the context of advanced nano-photonic devices.Comment: 10 pages, 7 figure
La Physique pour la Santé : du diagnostic à la thérapie
Pour une description précise de l'école "e2phy 2002", consulter le site http://e2phy.in2p3.fr. ISBN : 2-9510204-2-2 - Théorie, CASCe livre fait suite à l'école d'été de physique « e2phy 2002 » organisée à l'Université Claude Bernard Lyon 1 en août 2002. Cette école était la deuxième d'un cycle initié par l'IN2P3 (Institut National de Physique Nucléaire et de Physique des Particules) et le CEA (Commissariat à l'Énergie Atomique) pour lutter contre la désaffection des jeunes pour les études scientifiques. Elle a réuni des enseignants du second degré, des enseignants-chercheurs, des chercheurs, des hospitalo-universitaires et des ingénieurs. Le livre et son CD-ROM d'accompagnement (qui contient l'essentiel des présentations orales) donne une photographie des progrès, à l'instant t, de la physique, de la chimie, de la biologie et de la technologie appliquées à différents domaines de la médecine. Après des exposés d'intérêt général (physique médicale, interaction des ondes et des particules avec la matière biologique, signaux du vivant), des exposés sur des sujets où la physique joue un rôle essentiel sont abordés (diverses techniques d'imagerie médicale, utilisation des lasers, électroneurologie, modèles animaux, laboratoires sur puces, biomatériaux, médecine nucléaire, traitement des cancers par radiations ionisantes)
Subnanosecond spectral diffusion of a single quantum dot in a nanowire
We have studied spectral diffusion of the photoluminescence of a single CdSe
quantum dot inserted in a ZnSe nanowire. We have measured the characteristic
diffusion time as a function of pumping power and temperature using a recently
developed technique [G. Sallen et al, Nature Photon. \textbf{4}, 696 (2010)]
that offers subnanosecond resolution. These data are consistent with a model
where only a \emph{single} carrier wanders around in traps located in the
vicinity of the quantum dot
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