262 research outputs found
Classical Analog of Electromagnetically Induced Transparency
We present a classical analog for Electromagnetically Induced Transparency
(EIT). In a system of just two coupled harmonic oscillators subject to a
harmonic driving force we can reproduce the phenomenology observed in EIT. We
describe a simple experiment performed with two linearly coupled RLC circuits
which can be taught in an undergraduate laboratory class.Comment: 6 pages, two-column, 6 figures, submitted to the Am. J. Phy
Limitation of the modulation method to smooth wire guide roughness
It was recently demonstrated that wire guide roughness can be suppressed by
modulating the wire currents so that the atoms experience a time-averaged
potential without roughness. We theoretically study the limitations of this
technique. At low modulation frequency, we show that the longitudinal potential
modulation produces a heating of the cloud and we compute the heating rate. We
also give a quantum derivation of the rough conservative potential associated
with the micro-motion of the atoms. At large modulation frequency, we compute
the loss rate due to non adiabatic spin flip and show it presents resonnances
at multiple modulation frequencies. These studies show that the modulation
technique works for a wide range of experimental parameters. We also give
conditions to realise radio-frequency evaporative cooling in such a modulated
trap.Comment: 11 page
Super-poissonian photon statistics and correlations between pump and probe fields in Electromagnetically Induced Transparency
We have measured the photon statistics of pump and probe beams after
interaction with Rb atoms in a situation of Electromagnetically Induced
Transparency. Both fields present super-poissonian statistics and their
intensities become correlated, in good qualitative agreement with theoretical
predictions in which both fields are treated quantum-mechanically. The
intensity correlations measured are a first step towards the observation of
entanglement between the fields.Comment: 4 pages, two-column, 4 figures, first submitted to PRL on Aug. 6,
200
Evaporative cooling in a radio-frequency trap
A theoretical investigation for implementing a scheme of forced evaporative
cooling in radio-frequency (rf) adiabatic potentials is presented. Supposing
the atoms to be trapped by a rf field RF1, the cooling procedure is facilitated
using a second rf source RF2. This second rf field produces a controlled
coupling between the spin states dressed by RF1. The evaporation is then
possible in a pulsed or continuous mode. In the pulsed case, atoms with a given
energy are transferred into untrapped dressed states by abruptly switching off
the interaction. In the continuous case, it is possible for energetic atoms to
adiabatically follow the doubly-dressed states and escape out of the trap. Our
results also show that when the frequencies of the fields RF1 and RF2 are
separated by at least the Rabi frequency associated with RF1, additional
evaporation zones appear which can make this process more efficient.Comment: 12 pages, 11 figure
Trapping and cooling of rf-dressed atoms in a quadrupole magnetic field
6 pages, 6 figures; to appear in J. Phys. BInternational audienceWe observe the spontaneous evaporation of atoms confined in a bubble-like rf-dressed trap (Zobay and Garraway, 2001). The atoms are confined in a quadrupole magnetic trap and are dressed by a linearly polarized rf field. The evaporation is related to the presence of holes in the trap, at the positions where the rf coupling vanishes, due to its vectorial character. The final temperature results from a competition between residual heating and evaporation efficiency, which is controlled via the height of the holes with respect to the bottom of the trap. The experimental data are modeled by a Monte-Carlo simulation predicting a small increase in phase space density limited by the heating rate. This increase was within the phase space density determination uncertainty of the experiment
Non-destructive interferometric characterization of an optical dipole trap
A method for non-destructive characterization of a dipole trapped atomic
sample is presented. It relies on a measurement of the phase-shift imposed by
cold atoms on an optical pulse that propagates through a free space
Mach-Zehnder interferometer. Using this technique we are able to determine,
with very good accuracy, relevant trap parameters such as the atomic sample
temperature, trap oscillation frequencies and loss rates. Another important
feature is that our method is faster than conventional absorption or
fluorescence techniques, allowing the combination of high-dynamical range
measurements and a reduced number of spontaneous emission events per atom.Comment: 9 pages, 6 figures, submitted to PR
Continuous Cold-atom Inertial Sensor with Rotation Stability
We report the operation of a cold-atom inertial sensor which continuously
captures the rotation signal. Using a joint interrogation scheme, where we
simultaneously prepare a cold-atom source and operate an atom interferometer
(AI) enables us to eliminate the dead times. We show that such continuous
operation improves the short-term sensitivity of AIs, and demonstrate a
rotation sensitivity of in a
cold-atom gyroscope of Sagnac area. We also demonstrate a
rotation stability of at s of integration time,
which establishes the record for atomic gyroscopes. The continuous operation of
cold-atom inertial sensors will enable to benefit from the full sensitivity
potential of large area AIs, determined by the quantum noise limit.Comment: 4 pages, 3 figure
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