Interferometer-Type Structures for Guided Atoms

We experimentally demonstrate interferometer-type guiding structures for neutral atoms based on dipole potentials created by micro-fabricated optical systems. As a central element we use an array of atom waveguides being formed by focusing a red-detuned laser beam with an array of cylindrical microlenses. Combining two of these arrays, we realize X-shaped beam splitters and more complex systems like the geometries for Mach-Zehnder and Michelson-type interferometers for atoms.Comment: 4 pages, 6 figure

La préservation du patrimoine naturel littoral dans le processus de la gestion intégrée des zones côtières : éléments de réflexion pour l'élaboration d'un projet et perspectives

The coastal zone is an area of conflicting processes reflecting its position at the interface between the terrestrial and marine environments. This area needs further study and an enforcement of co-ordinated conservation policy for the implementation of effective protection. A multidisciplinary team (law, ecology, biology, and geography) has published a book, which assembles the elements of current politics involved with the preservation of the natural heritage of the coasts of mainland France. Part 1 deals on the definition of the coastal zone, the dispositions for the preservation of the natural heritage, the institutions concerned with its knowledge about and management and the objective criteria and methods for the choice or separation of zones to be protected. Part 2 gives the characteristic heritage aspects of the three coastal chosen regions. Part 3 gives perspectives to set up a more management model for the preservation of the natural heritage. It is necessary to have a clarification of current expertise resulting in a harmonization and institutional co-ordination of organisms linked to the coastal zone. The reform of the status of the CELRL increases its intervention in the maritime public domain. It offers prospects to consolidate this organization in its role in the protection of the littoral natural patrimonyInterface entre le milieu terrestre et le milieu marin, le littoral est une zone conflictuelle où les usages sont contradictoires, et un espace où il existe des besoins de connaissances et où il faut mettre en place une politique coordonnée de protection. Un ouvrage vient d'être réalisé par une équipe pluridisciplinaire (droit, écologie, biologie, géographie) en réponse au programme LITEAU du MATE. Il recense les éléments de la politique de préservation du patrimoine naturel de la France métropolitaine. Il prend pour exemples trois littoraux. Le Temps 1 s'ordonne autour des définitions du littoral, des institutions impliquées dans sa connaissance et sa gestion, des critères et méthodes objectives pour choisir ou délimiter des zones à préserver. Le Temps 2 traite des particularités patrimoniales des trois régions choisies. Le Temps 3 donne des perspectives pour construire un modèle de gestion satisfaisant du patrimoine naturel littoral à partir de l'analyse de l'existant. Les nombreuses interactions entre les intervenants multiples sur le littoral imposent une clarification des compétences, une harmonisation et une coordination institutionnelle. La réforme du statut du CELRL prévoit son intervention au domaine public maritime ; elle offre des perspectives pour le conforter dans son rôle d'acteur de la protection du patrimoine naturel littoral

1S-2S Spectrum of a Hydrogen Bose-Einstein Condensate

We calculate the two-photon 1S-2S spectrum of an atomic hydrogen Bose-Einstein condensate in the regime where the cold collision frequency shift dominates the lineshape. WKB and static phase approximations are made to find the intensities for transitions from the condensate to motional eigenstates for 2S atoms. The excited state wave functions are found using a mean field potential which includes the effects of collisions with condensate atoms. Results agree well with experimental data. This formalism can be used to find condensate spectra for a wide range of excitation schemes.Comment: 13 pages, 4 figure

Cold atom Clocks and Applications

This paper describes advances in microwave frequency standards using laser-cooled atoms at BNM-SYRTE. First, recent improvements of the $^{133}$Cs and $^{87}$Rb atomic fountains are described. Thanks to the routine use of a cryogenic sapphire oscillator as an ultra-stable local frequency reference, a fountain frequency instability of $1.6\times 10^{-14}\tau^{-1/2}$ where $\tau$ is the measurement time in seconds is measured. The second advance is a powerful method to control the frequency shift due to cold collisions. These two advances lead to a frequency stability of $2\times 10^{-16}$ at $50,000s for the first time for primary standards. In addition, these clocks realize the SI second with an accuracy of$7\times 10^{-16}$, one order of magnitude below that of uncooled devices. In a second part, we describe tests of possible variations of fundamental constants using$^{87}$Rb and$^{133}$Cs fountains. Finally we give an update on the cold atom space clock PHARAO developed in collaboration with CNES. This clock is one of the main instruments of the ACES/ESA mission which is scheduled to fly on board the International Space Station in 2008, enabling a new generation of relativity tests.Comment: 30 pages, 11 figure