305 research outputs found
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
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
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
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
Progress towards an accurate determination of the Boltzmann constant by Doppler spectroscopy
In this paper, we present significant progress performed on an experiment
dedicated to the determination of the Boltzmann constant, k, by accurately
measuring the Doppler absorption profile of a line in a gas of ammonia at
thermal equilibrium. This optical method based on the first principles of
statistical mechanics is an alternative to the acoustical method which has led
to the unique determination of k published by the CODATA with a relative
accuracy of 1.7 ppm. We report on the first measurement of the Boltzmann
constant by laser spectroscopy with a statistical uncertainty below 10 ppm,
more specifically 6.4 ppm. This progress results from improvements in the
detection method and in the statistical treatment of the data. In addition, we
have recorded the hyperfine structure of the probed saQ(6,3) rovibrational line
of ammonia by saturation spectroscopy and thus determine very precisely the
induced 4.36 (2) ppm broadening of the absorption linewidth. We also show that,
in our well chosen experimental conditions, saturation effects have a
negligible impact on the linewidth. Finally, we draw the route to future
developments for an absolute determination of with an accuracy of a few ppm.Comment: 22 pages, 11 figure
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
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)]
Hidden symmetry and nonlinear paraxial atom optics
A hidden symmetry of the nonlinear wave equation is exploited to analyse the
propagation of paraxial and uniform atom-laser beams in time-independent,
quadratic and cylindrical potentials varying smoothly along the propagation
axis. The quality factor and the paraxial ABCD formalism are generalized to
account exactly for mean-field interaction effects in such beams. Using an
approach based on moments, these theoretical tools provide a very simple and
yet exact picture of the interacting beam profile evolution. Guided atom laser
experiments are discussed. This treatment addresses simultaneously optical and
atomic beams in a unified manner, exploiting the formal analogy between
nonlinear optics and nonlinear paraxial atom optics.Comment: Final Version. Changes in the abstract and minor changes in the text
with respect to the version published in PR
The Dipole Coupling of Atoms and Light in Gravitational Fields
The dipole coupling term between a system of N particles with total charge
zero and the electromagnetic field is derived in the presence of a weak
gravitational field. It is shown that the form of the coupling remains the same
as in flat space-time if it is written with respect to the proper time of the
observer and to the measurable field components. Some remarks concerning the
connection between the minimal and the dipole coupling are given.Comment: 10 pages, LaTe
Ramsey interferometry with oppositely detuned fields
We report a narrowing of the interference pattern obtained in an atomic
Ramsey interferometer if the two separated fields have different frequency and
their phase difference is controlled. The width of the Ramsey fringes depends
inversely on the free flight time of ground state atoms before entering the
first field region in addition to the time between the fields. The effect is
stable also for atomic wavepackets with initial position and momentum
distributions and for realistic mode functions.Comment: 6 pages, 6 figure
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