643 research outputs found
Differential phase extraction in an atom gradiometer
We present here a method for the extraction of the differential phase of an
atom gradiometer that exploits the correlation of the vibration signal measured
by an auxiliary classical sensor, such as a seismometer or an accelerometer. We
show that sensitivities close to the quantum projection noise limit can be
reached, even when the vibration noise induces phase fluctuations larger than
2. This method doesn't require the correlation between the atomic and
classical signals to be perfect and allows for an exact determination of the
differential phase, with no bias. It can also be applied to other
configurations of differential interferometers, such as for instance
gyrometers, conjugate interferometers for the measurement of the fine structure
constant, or differential accelerometers for tests of the equivalence principle
or detection of gravitational waves
Enhancing the area of a Raman atom interferometer using a versatile double-diffraction technique
IIn this paper we demonstrate a new scheme for Raman transitions which
realize a symmetric momentum-space splitting of , deflecting the
atomic wave-packets into the same internal state. Combining the advantages of
Raman and Bragg diffraction, we achieve a three pulse state labelled
interferometer, intrinsically insensitive to the main systematics and
applicable to all kind of atomic sources. This splitting scheme can be extended
to momentum transfer by a multipulse sequence and is implemented
on a interferometer. We demonstrate the area enhancement by
measuring inertial forces
A simple laser system for atom interferometry
We present here a simple laser system for a laser cooled atom interferometer,
where all functions (laser cooling, interferometry and detection) are realized
using only two extended cavity laser diodes, amplified by a common tapered
amplifier. One laser is locked by frequency modulation transfer spectroscopy,
the other being phase locked with an offset frequency determined by an
Field-Programmable Gate Array (FPGA) controlled Direct Digital Synthesizer
(DDS), which allows for efficient and versatile tuning of the laser frequency.
Raman lasers are obtained with a double pass acousto-optic modulator. We
demonstrate a gravimeter using this laser system, with performances close to
the state of the art
Coherent population trapping in a Raman atom interferometer
We investigate the effect of coherent population trapping (CPT) in an atom
inter-ferometer gravimeter based on the use of stimulated Raman transitions. We
find that CPT leads to significant phase shifts, of order of a few mrad, which
may compromise the accuracy of inertial measurements. We show that this effect
is rejected by the k-reversal technique, which consists in averaging inertial
measurements performed with two opposite orientations of the Raman wavevector
k, provided that internal states at the input of the interferometer are kept
identical for both configurations
Active Control of Laser Wavefronts in Atom Interferometers
Wavefront aberrations are identified as a major limitation in quantum
sensors. They are today the main contribution in the uncertainty budget of best
cold atom interferometers based on two-photon laser beam splitters, and
constitute an important limit for their long-term stability, impeding these
instruments from reaching their full potential. Moreover, they will also remain
a major obstacle in future experiments based on large momentum beam splitters.
In this article, we tackle this issue by using a deformable mirror to control
actively the laser wavefronts in atom interferometry. In particular, we
demonstrate in an experimental proof of principle the efficient correction of
wavefront aberrations in an atomic gravimeter
Accelerometer using atomic waves for space applications
The techniques of laser cooling combined with atom interferometry make
possible the realization of very sensitive and accurate inertial sensors like
gyroscopes or accelerometers. Besides earth-based developments, the use of
these techniques in space should provide extremely high sensitivity for
research in fundamental physics, Earth's observation and exploration of the
solar system
Raman laser spectroscopy of Wannier Stark states
Raman lasers are used as a spectroscopic probe of the state of atoms confined
in a shallow 1D vertical lattice. For long enough laser pulses, resolved
transitions in the bottom band of the lattice between Wannier Stark states
corresponding to neighboring wells are observed. Couplings between such states
are measured as a function of the lattice laser intensity and compared to
theoretical predictions, from which the lattice depth can be extracted. Limits
to the linewidth of these transitions are investigated. Transitions to higher
bands can also be induced, as well as between transverse states for tilted
Raman beams. All these features allow for a precise characterization of the
trapping potential and for an efficient control of the atoms external degrees
of freedom
Stability comparison of two absolute gravimeters: optical versus atomic interferometers
We report the direct comparison between the stabilities of two mobile
absolute gravimeters of different technology: the LNE-SYRTE Cold Atom
Gravimeter and FG5X\#216 of the Universit\'e du Luxembourg. These instruments
rely on two different principles of operation: atomic and optical
interferometry. The comparison took place in the Walferdange Underground
Laboratory for Geodynamics in Luxembourg, at the beginning of the last
International Comparison of Absolute Gravimeters, ICAG-2013. We analyse a 2h10
duration common measurement, and find that the CAG shows better immunity with
respect to changes in the level of vibration noise, as well as a slightly
better short term stability.Comment: 6 page
State labelling Wannier-Stark atomic interferometers
Using cold 87Rb atoms trapped in a 1D-optical lattice, atomic interferometers
involving coherent superpositions between different Wannier-Stark atomic states
are realized. Two di fferent kinds of trapped interferometer schemes are
presented: a Ramsey-type interferometer sensitive both to clock frequency and
external forces, and a symmetric accordion-type interferometer, sensitive to
external forces only. We evaluate the limits in terms of sensitivity and
accuracy of those schemes and discuss their application as force sensors. As a
first step, we apply these interferometers to the measurement of the Bloch
frequency and the demonstration of a compact gravimeter.Comment: 11 page
Quectonewton local force sensor
We report on the realization of a quantum sensor based on trapped atom
interferometry in an optical lattice for the measurement of atom-surface
interactions, with sub-micrometer-level control of the mean atom-surface
separation distance. The force sensor reaches a short-term sensitivity of 3.4 x
10 --28 N at 1 s and a long-term stability of 4 qN (4 x 10 --30 N). We perform
force measurements in the 0-300 m range, and despite significant stray
forces caused by adsorbed atoms on the surface, we obtain evidence of the
Casimir-Polder force. Short-range forces are one of the many frontiers of
modern physics [1, 2]. In the submillimeter scales, quantum electrodynamics
(QED) interactions are dominant, and give rise in the case of atom-surface
interactions to the Casimir-Polder force [3]. Since the first highlight of this
force [4], several different methods [5] have been able to bring out
Casimir-Polder forces, notably by measuring the transmission of an atomic beam
through a micronsized cavity [6], diffracting matter waves on a surface [7] or
performing spectroscopy in vapor cells [8, 9]. However these approaches have
struggled to achieve the high measurement sensitivity required to detect the
very weak forces involved all while maintaining a good understanding of the
setup geometry, particularly the distance separating atoms from the surface.
Few experiments have achieved measuring Casimir-Polder forces while controlling
directly the atom-surface distance. In the range from tens to hundreds of
nanometers, the Casimir-Polder potential was measured directly by reflecting
the atoms on an evanescent field [10, 11]. I
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