Exact phase shifts for atom interferometry

In the case of an external Hamiltonian at most quadratic in position and momentum operators, we use the ABCD formulation of atom optics to establish an exact analytical phase shift expression for atom interferometers with arbitrary spatial or temporal beam splitter configurations. This result is expressed in terms of coordinates and momenta of the wave packet centers at the interaction vertices only.Comment: 11 pages, 3 figures, submitted to Phys. Lett.

Space-time sensors using multiple-wave atom levitation

The best clocks to date control the atomic motion by trapping the sample in an optical lattice and then interrogate the atomic transition by shining on these atoms a distinct laser of controlled frequency. In order to perform both tasks simultaneously and with the same laser field, we propose to use instead the levitation of a Bose-Einstein condensate through multiple-wave atomic interferences. The levitating condensate experiences a coherent localization in momentum and a controlled diffusion in altitude. The sample levitation is bound to resonance conditions used either for frequency or for acceleration measurements. The chosen vertical geometry solves the limitations imposed by the sample free fall in previous optical clocks using also atomic interferences. This configuration yields multiple-wave interferences enabling levitation and enhancing the measurement sensitivity. This setup, analogous to an atomic resonator in momentum space, constitutes an attractive alternative to existing atomic clocks and gravimeters.Comment: 5 pages, 4 figures.Final versio

Reforming the international system of units: On our way to redefine the base units solely from fundamental constants and beyond

Our purpose is to offer a logical analysis of the system of units and to explore possible paths towards a consistent and unified system with an original perspective. The path taken here builds on the fact that, thanks to optical or matter-wave interferometry, any measurement can be reduced to a dimensionless phase measurement and we follow this simple guiding line. We finally show how one could progress even further on the path of a synthetic framework for fundamental metrology based upon pure geometry in five dimensions

Speckle noise reduction techniques for high-dynamic range imaging

High-dynamic range imaging from space in the visible, aiming in particular at the detection of terrestrial exoplanets, necessitates not only the use of a coronagraph, but also of adaptive optics to correct optical defects in real time. Indeed, these defects scatter light and give birth to speckles in the image plane. Speckles can be cancelled by driving a deformable mirror to measure and compensate wavefront aberrations. In a first approach, targeted speckle nulling, speckles are cancelled iteratively by starting with the brightest ones. This first method has demonstrated a contrast better than 1e9 in laboratory. In a second approach, zonal speckle nulling, the total energy of speckles is minimized in a given zone of the image plane. This second method has the advantage to tackle simultaneously all speckles from the targeted zone, but it still needs better experimental demonstration.Comment: 7 pages, 3 figures, in Optical techniques for direct imaging of exoplanets (a special issue of Comptes Rendus de Physique

The theory of quantum levitators

We develop a unified theory for clocks and gravimeters using the interferences of multiple atomic waves put in levitation by traveling light pulses. Inspired by optical methods, we exhibit a propagation invariant, which enables to derive analytically the wave function of the sample scattering on the light pulse sequence. A complete characterization of the device sensitivity with respect to frequency or to acceleration measurements is obtained. These results agree with previous numerical simulations and confirm the conjecture of sensitivity improvement through multiple atomic wave interferences. A realistic experimental implementation for such clock architecture is discussed.Comment: 11 pages, 6 Figures. Minor typos corrected. Final versio

Transdet: a matched-filter based algorithm for transit detection - application to simulated COROT light curves

We present a matched-filter based algorithm for transit detection and its application to simulated COROT light curves. This algorithm stems from the work by Bord\'e, Rouan & L\'eger (2003). We describe the different steps we intend to take to discriminate between planets and stellar companions using the three photometric bands provided by COROT. These steps include the search for secondary transits, the search for ellipsoidal variability, and the study of transit chromaticity. We also discuss the performance of this approach in the context of blind tests organized inside the COROT exoplanet consortium.Comment: 6 pages, 4 figures, in Transiting Extrasolar Planets Workshop, meeting held in Heidelberg, 25-28 September 200

6-axis inertial sensor using cold-atom interferometry

We have developed an atom interferometer providing a full inertial base. This device uses two counter-propagating cold-atom clouds that are launched in strongly curved parabolic trajectories. Three single Raman beam pairs, pulsed in time, are successively applied in three orthogonal directions leading to the measurement of the three axis of rotation and acceleration. In this purpose, we introduce a new atom gyroscope using a butterfly geometry. We discuss the present sensitivity and the possible improvements.Comment: submitted to PR

The CoRoT Exoplanet program : status & results

The CoRoT satellite is the first instrument hunting for planets from space. We will review the status of the CoRoT/Exoplanet program. We will then present the CoRoT exoplanetary systems and how they widen the range of properties of the close-in population and contribute to our understanding of the properties of planets.Comment: 10 pages, Proceeding of Haute Provence Observatory Colloquium (23-27 August 2010