347 research outputs found
Photonic properties of one-dimensionally-ordered cold atomic vapors under conditions of electromagnetically induced transparency
We experimentally study the photonic properties of a cold-atom sample trapped
in a one-dimensional optical lattice under the conditions of
electromagnetically induced transparency. We show that such a medium has two
photonic band gaps. One of them is in the transparency window and gives rise to
a Bragg mirror, which is spectrally very narrow and dynamically tunable. We
discuss the advantages and the limitations of this system. As an illustration
of a possible application we demonstrate a two-port all-optical switch
Measurement of the Gravity-Field Curvature by Atom Interferometry
We present the first direct measurement of the gravity-field curvature based
on three conjugated atom interferometers. Three atomic clouds launched in the
vertical direction are simultaneously interrogated by the same atom
interferometry sequence and used to probe the gravity field at three equally
spaced positions. The vertical component of the gravity-field curvature
generated by nearby source masses is measured from the difference between
adjacent gravity gradient values. Curvature measurements are of interest in
geodesy studies and for the validation of gravitational models of the
surrounding environment. The possibility of using such a scheme for a new
determination of the Newtonian constant of gravity is also discussed.Comment: 5 pages, 3 figure
Measurement of a Mixed Spin Channel Feshbach Resonance in Rubidium 87
We report on the observation of a mixed spin channel Feshbach resonance at
the low magnetic field value of (9.09 +/- 0.01) G for a mixture of |2,-1> and
|1,+1> states in 87Rb. This mixture is important for applications of
multi-component BECs of 87Rb, e.g. in spin mixture physics and for quantum
entanglement. Values for position, height and width of the resonance are
reported and compared to a recent theoretical calculation of this resonance.Comment: 4 pages, 3 figures minor changes, actualized citation
Determination of the Newtonian Gravitational Constant Using Atom Interferometry
We present a new measurement of the Newtonian gravitational constant G based
on cold atom interferometry. Freely falling samples of laser-cooled rubidium
atoms are used in a gravity gradiometer to probe the field generated by nearby
source masses. In addition to its potential sensitivity, this method is
intriguing as gravity is explored by a quantum system. We report a value of
G=6.667 10^{-11} m^{3} kg^{-1} s^{-2}, estimating a statistical uncertainty of
0.011 10^{-11} m^{3} kg^{-1} s^{-2} and a systematic uncertainty of
0.003 10^{-11} m^{3} kg^{-1} s^{-2}. The long-term stability of the instrument
and the signal-to-noise ratio demonstrated here open interesting perspectives
for pushing the measurement accuracy below the 100 ppm level.Comment: 4 figure
A portable laser system for high precision atom interferometry experiments
We present a modular rack-mounted laser system for the cooling and
manipulation of neutral rubidium atoms which has been developed for a portable
gravimeter based on atom interferometry that will be capable of performing high
precision gravity measurements directly at sites of geophysical interest. This
laser system is constructed in a compact and mobile design so that it can be
transported to different locations, yet it still offers improvements over many
conventional laboratory-based laser systems. Our system is contained in a
standard 19" rack and emits light at five different frequencies simultaneously
on up to 12 fibre ports at a total output power of 800 mW. These frequencies
can be changed and switched between ports in less than a microsecond. The setup
includes two phase-locked diode lasers with a phase noise spectral density of
less than 1 \mu rad/sqrt(Hz) in the frequency range in which our gravimeter is
most sensitive to noise. We characterize this laser system and evaluate the
performance limits it imposes on an interferometer.Comment: 8 pages, 11 figures; The final publication is available at
http://www.springerlink.co
Precision measurement of gravity with cold atoms in an optical lattice and comparison with a classical gravimeter
We report on a high precision measurement of gravitational acceleration using
ultracold strontium atoms trapped in a vertical optical lattice. Using
amplitude modulation of the lattice intensity, an uncertainty was reached by measuring at the 5 harmonic of the Bloch
oscillation frequency. After a careful analysis of systematic effects, the
value obtained with this microscopic quantum system is consistent with the one
we measured with a classical absolute gravimeter at the same location. This
result is of relevance for the recent interpretation of related experiments as
tests of gravitational redshift and opens the way to new tests of gravity at
micrometer scale.Comment: 4 pages, 4 figure
Quantum test of the equivalence principle for atoms in superpositions of internal energy eigenstates
The Einstein Equivalence Principle (EEP) has a central role in the
understanding of gravity and space-time. In its weak form, or Weak Equivalence
Principle (WEP), it directly implies equivalence between inertial and
gravitational mass. Verifying this principle in a regime where the relevant
properties of the test body must be described by quantum theory has profound
implications. Here we report on a novel WEP test for atoms. A Bragg atom
interferometer in a gravity gradiometer configuration compares the free fall of
rubidium atoms prepared in two hyperfine states and in their coherent
superposition. The use of the superposition state allows testing genuine
quantum aspects of EEP with no classical analogue, which have remained
completely unexplored so far. In addition, we measure the Eotvos ratio of atoms
in two hyperfine levels with relative uncertainty in the low ,
improving previous results by almost two orders of magnitude.Comment: Accepted for publication in Nature Communicatio
A compact and efficient strontium oven for laser-cooling experiments
Here we describe a compact and efficient strontium oven well suited for
laser-cooling experiments. Novel design solutions allowed us to produce a
collimated strontium atomic beam with a flux of 1.0\times10^13 s^-1 cm^-2 at
the oven temperature of 450 {\deg}C, reached with an electrical power
consumption of 36 W. The oven is based on a stainless-steel reservoir, filled
with 6 g of metallic strontium, electrically heated in a vacuum environment by
a tantalum wire threaded through an alumina multi-bore tube. The oven can be
hosted in a standard DN40CF cube and has an estimated continuous operation
lifetime of 10 years. This oven can be used for other alkali and alkaline earth
metals with essentially no modifications.Comment: 6 pages, 6 figures, Review of Scientific Instruments, in pres
Sensitivity limits of a Raman atom interferometer as a gravity gradiometer
We evaluate the sensitivity of a dual cloud atom interferometer to the
measurement of vertical gravity gradient. We study the influence of most
relevant experimental parameters on noise and long-term drifts. Results are
also applied to the case of doubly differential measurements of the
gravitational signal from local source masses. We achieve a short term
sensitivity of 3*10^(-9) g/Hz^(-1/2) to differential gravity acceleration,
limited by the quantum projection noise of the instrument. Active control of
the most critical parameters allows to reach a resolution of 5*10^(-11) g after
8000 s on the measurement of differential gravity acceleration. The long term
stability is compatible with a measurement of the gravitational constant G at
the level of 10^(-4) after an integration time of about 100 hours.Comment: 19 pages, 20 figure
Sensitive gravity-gradiometry with atom interferometry: progress towards an improved determination of the gravitational constant
We here present a high sensitivity gravity-gradiometer based on atom
interferometry. In our apparatus, two clouds of laser-cooled rubidium atoms are
launched in fountain configuration and interrogated by a Raman interferometry
sequence to probe the gradient of gravity field. We recently implemented a
high-flux atomic source and a newly designed Raman lasers system in the
instrument set-up. We discuss the applications towards a precise determination
of the Newtonian gravitational constant G. The long-term stability of the
instrument and the signal-to-noise ratio demonstrated here open interesting
perspectives for pushing the measurement precision below the 100 ppm level
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