101 research outputs found
Precision measurement of light shifts in a single trapped Ba ion
Using a single trapped barium ion we have developed an rf spectroscopy
technique to measure the ratio of the off-resonant vector ac Stark effect (or
light shift) in the 6S_{1/2} and 5D_{3/2} states to 0.1% precision. We find R =
Delta_S / Delta_D = -11.494(13) at 514.531 nm where Delta_{S,D} are the light
shifts of the m = +/- 1/2 splittings due to circularly polarized light.
Comparison of this result with an ab initio calculation of R would yield a new
test of atomic theory. By appropriately choosing an off-resonant light shift
wavelength one can emphasize the contribution of one or a few dipole matrix
elements and precisely determine their values.Comment: 4 pages, 5 figures, in submission to PR
Low and high intensity velocity selective coherent population trapping in a two-level system
An experimental investigation is made of sub-recoil cooling by velocity
selective coherent population trapping in a two-level system in Sr. The
experiment is carried out using the narrow linewidth intercombination line at
689 nm. Here, the ratio between the recoil shift and the linewidth is as high
as 0.64. We show that, on top of a broader momentum profile, subrecoil features
develop, whose amplitude is strongly dependent on the detuning from resonance.
We attribute this structure to a velocity selective coherent population
trapping mechanism. We also show that the population trapping phenomenon leads
to complex momentum profiles in the case of highly saturated transitions,
displaying a multitude of subrecoil features at integer multiples of the recoil
momentum.Comment: 6 pages and 7 figure
Fluctuation properties of laser light after interaction with an atomic system: comparison between two-level and multilevel atomic transitions
The complex internal atomic structure involved in radiative transitions has
an effect on the spectrum of fluctuations (noise) of the transmitted light. A
degenerate transition has different properties in this respect than a pure
two-level transition. We investigate these variations by studying a certain
transition between two degenerate atomic levels for different choices of the
polarization state of the driving laser. For circular polarization,
corresponding to the textbook two-level atom case, the optical spectrum shows
the characteristic Mollow triplet for strong laser drive, while the
corresponding noise spectrum exhibits squeezing in some frequency ranges. For a
linearly polarized drive, corresponding to the case of a multilevel system,
additional features appear in both optical and noise spectra. These differences
are more pronounced in the regime of a weakly driven transition: whereas the
two-level case essentially exhibits elastic scattering, the multilevel case has
extra noise terms related to spontaneous Raman transitions. We also discuss the
possibility to experimentally observe these predicted differences for the
commonly encountered case where the laser drive has excess noise in its phase
quadrature.Comment: New version. Accepted for publication in Physical Review
A nonadiabatic semi-classical method for dynamics of atoms in optical lattices
We develop a semi-classical method to simulate the motion of atoms in a
dissipative optical lattice. Our method treats the internal states of the atom
quantum mechanically, including all nonadiabatic couplings, while position and
momentum are treated as classical variables. We test our method in the
one-dimensional case. Excellent agreement with fully quantum mechanical
simulations is found. Our results are much more accurate than those of earlier
semi-classical methods based on the adiabatic approximation.Comment: 7 pages, 5 figures, submitted to European Physical Journal
Relativistic Coupled-Cluster Theory of Atomic Parity Nonconservation: Application to Ba
We report the result of our {\it ab initio} calculation of the parity nonconserving electric dipole transition amplitude in
based on relativistic coupled-cluster theory. Considering
single, double and partial triple excitations, we have achieved an accuracy of
less than one percent. If the accuracy of our calculation can be matched by the
proposed parity nonconservation experiment in Ba for the above
transition,then the combination of the two results would provide an independent
non accelerator test of the Standard Model of particle physics.Comment: 4 pages, 1 figure, Submitted to PR
Polarization entangled photon-pair source based on quantum nonlinear photonics and interferometry
We present a versatile, high-brightness, guided-wave source of polarization
entangled photons, emitted at a telecom wavelength. Photon-pairs are generated
using an integrated type-0 nonlinear waveguide, and subsequently prepared in a
polarization entangled state via a stabilized fiber interferometer. We show
that the single photon emission wavelength can be tuned over more than 50 nm,
whereas the single photon spectral bandwidth can be chosen at will over more
than five orders of magnitude (from 25 MHz to 4 THz). Moreover, by performing
entanglement analysis, we demonstrate a high degree of control of the quantum
state via the violation of the Bell inequalities by more than 40 standard
deviations. This makes this scheme suitable for a wide range of quantum optics
experiments, ranging from fundamental research to quantum information
applications. We report on details of the setup, as well as on the
characterization of all included components, previously outlined in F. Kaiser
et al. (2013 Laser Phys. Lett. 10, 045202).Comment: 16 pages, 7 figure
Influence of the lattice topography on a three-dimensional, controllable Brownian motor
We study the influence of the lattice topography and the coupling between
motion in different directions, for a three-dimensional Brownian motor based on
cold atoms in a double optical lattice. Due to controllable relative spatial
phases between the lattices, our Brownian motor can induce drifts in arbitrary
directions. Since the lattices couple the different directions, the relation
between the phase shifts and the directionality of the induced drift is non
trivial. Here is therefore this relation investigated experimentally by
systematically varying the relative spatial phase in two dimensions, while
monitoring the vertically induced drift and the temperature. A relative spatial
phase range of 2pi x 2pi is covered. We show that a drift, controllable both in
speed and direction, can be achieved, by varying the phase both parallel and
perpendicular to the direction of the measured induced drift. The experimental
results are qualitatively reproduced by numerical simulations of a simplified,
classical model of the system
Thermodynamics of quantum degenerate gases in optical lattices
The entropy-temperature curves are calculated for non-interacting Bose and
Fermi gases in a 3D optical lattice. These curves facilitate understanding of
how adiabatic changes in the lattice depth affect the temperature, and we
demonstrate regimes where the atomic sample can be significantly heated or
cooled by the loading process. We assess the effects of interactions on a Bose
gas in a deep optical lattice, and show that interactions ultimately limit the
extent of cooling that can occur during lattice loading.Comment: 6 pages, 4 figures. Submitted to proceedings of Laser Physics 2006
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