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

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

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

Matter-wave cavity gravimeter

We propose a gravimeter based on a matter-wave resonant cavity loaded with a Bose-Einstein condensate and closed with a sequence of periodic Raman pulses. The gravimeter sensitivity increases quickly with the number of cycles experienced by the condensate inside the cavity. The matter wave is refocused thanks to a spherical wave-front of the Raman pulses. This provides a transverse confinement of the condensate which is discussed in terms of a stability analysis. We develop the analogy of this device with a resonator in momentum space for matter waves.Comment: 15 pages, 6 Figures. The expression for the atomic mirror focal length has been corrected. Other minor corrections and actualizations to the previously published versio

THE "FREELY" FALLING TWO-LEVEL ATOM IN A RUNNING LASER WAVE

The time evolution of a two-level atom which is simultaneously exposed to the field of a running laser wave and a homogeneous gravitational field is studied. The result of the coupled dynamics of internal transitions and center-of-mass motion is worked out exactly. Neglecting spontaneous emission and performing the rotating wave approximation we derive the complete time evolution operator in an algebraical way by using commutation relations. The result is discussed with respect to the physical implications. In particular the long time and short time behaviour is physically analyzed in detail. The breakdown of the Magnus perturbation expansion is shown.Comment: 14 Pages, Late

A catalog of bright calibrator stars for 200-meter baseline near-infrared stellar interferometry

We present in this paper a catalog of reference stars suitable for calibrating infrared interferometric observations. In the K band, visibilities can be calibrated with a precision of 1% on baselines up to 200 meters for the whole sky, and up to 300 meters for some part of the sky. This work, extending to longer baselines a previous catalog compiled by Borde et al. (2002), is particularly well adapted to hectometric-class interferometers such as the Very Large Telescope Interferometer (VLTI, Glindemann et al. 2003) or the CHARA array (ten Brummelaar et al. 2003) when observing well resolved, high surface brightness objects (K<8). We use the absolute spectro-photometric calibration method introduced by Cohen et al. (1999) to derive the angular diameters of our new set of 948 G8--M0 calibrator stars extracted from IRAS, 2MASS and MSX catalogs. Angular stellar diameters range from 0.6 mas to 1.8 mas (median is 1.1 mas) with a median precision of 1.35%. For both the northern and southern hemispheres, the closest calibrator star is always less than 10 degree away.Comment: 9 pages, 7 figures, submitted to A&A. The full catalog can be found in http://calys.obspm.fr/~merand/Files/MerandEtAlCatalogue.tx

Atom gravimeters and gravitational redshift

In a recent paper, H. Mueller, A. Peters and S. Chu [A precision measurement of the gravitational redshift by the interference of matter waves, Nature 463, 926-929 (2010)] argued that atom interferometry experiments published a decade ago did in fact measure the gravitational redshift on the quantum clock operating at the very high Compton frequency associated with the rest mass of the Caesium atom. In the present Communication we show that this interpretation is incorrect.Comment: 2 pages, Brief Communication appeared in Nature (2 September 2010

Theoretical tools for atom laser beam propagation

We present a theoretical model for the propagation of non self-interacting atom laser beams. We start from a general propagation integral equation, and we use the same approximations as in photon optics to derive tools to calculate the atom laser beam propagation. We discuss the approximations that allow to reduce the general equation whether to a Fresnel-Kirchhoff integral calculated by using the stationary phase method, or to the eikonal. Within the paraxial approximation, we also introduce the ABCD matrices formalism and the beam quality factor. As an example, we apply these tools to analyse the recent experiment by Riou et al. [Phys. Rev. Lett. 96, 070404 (2006)]

Modelling solar-like variability for the detection of Earth-like planetary transits. II. Performance of the three-spot modelling, harmonic function fitting, iterative nonlinear filtering, and sliding boxcar filtering

Copyright © The European Southern Observatory (ESO)Aims. As an extension of a previous work, we present a comparison of four methods of filtering solar-like variability to increase the efficiency of detection of Earth-like planetary transits by means of box-shaped transit finder algorithms. Two of these filtering methods are the harmonic fitting method and the iterative nonlinear filter that, coupled respectively with the box least-square (BLS) and box maximum likelihood algorithms, demonstrated the best performance during the first detection blind test organised inside the CoRoT consortium. The third method, the 3-spot model, is a simplified physical model of Sun-like variability and the fourth is a simple sliding boxcar filter. Methods. We apply a Monte Carlo approach by simulating a large number of 150-day light curves (as for CoRoT long runs) for different planetary radii, orbital periods, epochs of the first transit, and standard deviations of the photon shot noise. Stellar variability is given by the total solar irradiance variations as observed close to the maximum of solar cycle 23. After filtering solar variability, transits are searched for by means of the BLS algorithm. Results. We find that the iterative nonlinear filter is the best method for filtering light curves of solar-like stars when a suitable window can be chosen. As the performance of this filter depends critically on the length of its window, we point out that the window must be as long as possible, according to the magnetic activity level of the star. We show an automatic method to choose the extension of the filter window from the power spectrum of the light curves. Conclusions. The iterative nonlinear filter, when used with a suitable choice of its window, has a better performance than more complicated and computationally intensive methods of fitting solar-like variability, like the 200-harmonic fitting or the 3-spot model

Coherence Properties of Guided-Atom Interferometers

We present a detailed investigation of the coherence properties of beam splitters and Mach-Zehnder interferometers for guided atoms. It is demonstrated that such a setup permits coherent wave packet splitting and leads to the appearance of interference fringes. We study single-mode and thermal input states and show that even for thermal input states interference fringes can be clearly observed, thus demonstrating the multimode operation and the robustness of the interferometer.Comment: 4 pages, 4 figure