15 research outputs found
Noise sensitivity of an atomic velocity sensor
We use Bloch oscillations to accelerate coherently Rubidium atoms. The
variation of the velocity induced by this acceleration is an integer number
times the recoil velocity due to the absorption of one photon. The measurement
of the velocity variation is achieved using two velocity selective Raman
pi-pulses: the first pulse transfers atoms from the hyperfine state 5S1/2 |F=2,
mF=0> to 5S1/2, |F=1, mF = 0> into a narrow velocity class. After the
acceleration of this selected atomic slice, we apply the second Raman pulse to
bring the resonant atoms back to the initial state 5S1/2, |F=2, mF = 0>. The
populations in (F=1 and F=2) are measured separately by using a one-dimensional
time-of-flight technique. To plot the final velocity distribution we repeat
this procedure by scanning the Raman beam frequency of the second pulse. This
two pi-pulses system constitutes then a velocity sensor. Any noise in the
relative phase shift of the Raman beams induces an error in the measured
velocity. In this paper we present a theoretical and an experimental analysis
of this velocity sensor, which take into account the phase fluctuations during
the Raman pulses
Theoretical Analysis of a Large Momentum Beamsplitter using Bloch Oscillations
In this paper, we present the implementation of Bloch oscillations in an
atomic interferometer to increase the separation of the two interfering paths.
A numerical model, in very good agreement with the experiment, is developed.
The contrast of the interferometer and its sensitivity to phase fluctuations
and to intensity fluctuations are also calculated. We demonstrate that the
sensitivity to phase fluctuations can be significantly reduced by using a
suitable arrangement of Bloch oscillations pulses
Proposal for new experimental schemes to realize the Avogadro constant
We propose two experimental schemes to determine and so to realize the
Avogadro constant at the level of 10 or better with a watt
balance experiment and a cold atom experiment measuring (where is
the Planck constant and the mass of the atom ). We give some
prospects about achievable uncertainties and we discuss the opportunity to test
the existence of possible unknown correction factors for the Josephson effect
and quantum Hall effect
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
A promising method for the measurement of the local acceleration of gravity using Bloch oscillations of ultracold atoms in a vertical standing wave
An obvious determination of the local acceleration of gravity g can be
deduced from the measurement of the velocity of falling atoms
using a Ï-Ï pulses sequence of stimulated Raman
transitions. By using a vertical standing wave to hold atoms
against gravity, we expect to improve the relative accuracy by
increasing the upholding time in the gravity field and to
minimize the systematic errors induced by inhomogeneous fields,
owing to the very small spatial amplitude of the atomic
center-of-mass wavepacket periodic motion. We also propose to use
such an experimental setup nearby a Watt balance. By exploiting
the (h is the Planck constant) dependence of the Bloch
frequency, this should provide a way to link a macroscopic mass
to an atomic mass
Accélération d'atomes ultrafroids: vers une mesure de hM
Le but de l'expérience est la mesure de la vitesse de recul
d'atomes de rubidium. Une determination du rapport
ainsi que de la constante de structure fine peuvent en
ĂȘtre dĂ©duites. Les mesures prĂ©liminaires que nous avons effectuĂ©es
conduisent à une incertitude de  ppm sur