487 research outputs found
Theory of dark resonances for alkali vapors in a buffer-gas cell
We develop an analytical theory of dark resonances that accounts for the full
atomic-level structure, as well as all field-induced effects such as coherence
preparation, optical pumping, ac Stark shifts, and power broadening. The
analysis uses a model based on relaxation constants that assumes the total
collisional depolarization of the excited state. A good qualitative agreement
with experiments for Cs in Ne is obtained.Comment: 16 pages; 7 figures; revtex4. Accepted for publication in PR
Bichromatic electromagnetically induced transparency in cold rubidium atoms
In a three-level atomic system coupled by two equal-amplitude laser fields
with a frequency separation 2, a weak probe field exhibits a
multiple-peaked absorption spectrum with a constant peak separation .
The corresponding probe dispersion exhibits steep normal dispersion near the
minimum absorption between the multiple absorption peaks, which leads to
simultaneous slow group velocities for probe photons at multiple frequencies
separated by . We report an experimental study in such a
bichromatically coupled three-level system in cold Rb atoms.
The multiple-peaked probe absorption spectra under various experimental
conditions have been observed and compared with the theoretical calculations.Comment: RevTex, 4 pages, 6 figures, Email address: [email protected]
Cold atoms in videotape micro-traps
We describe an array of microscopic atom traps formed by a pattern of
magnetisation on a piece of videotape. We describe the way in which cold atoms
are loaded into one of these micro-traps and how the trapped atom cloud is used
to explore the properties of the trap. Evaporative cooling in the micro-trap
down to a temperature of 1 microkelvin allows us to probe the smoothness of the
trapping potential and reveals some inhomogeneity produced by the magnetic
film. We discuss future prospects for atom chips based on microscopic
permanent-magnet structures.Comment: Submitted for EPJD topical issue "Atom chips: manipulating atoms and
molecules with microfabricated structures
A surface-patterned chip as a strong source of ultracold atoms for quantum technologies
Laser-cooled atoms are central to modern precision measurements. They are also increasingly important as an enabling technology for experimental cavity quantum electrodynamics, quantum information processing and matter–wave interferometry. Although significant progress has been made in miniaturizing atomic metrological devices, these are limited in accuracy by their use of hot atomic ensembles and buffer gases. Advances have also been made in producing portable apparatus that benefits from the advantages of atoms in the microkelvin regime. However, simplifying atomic cooling and loading using microfabrication technology has proved difficult. In this Letter we address this problem, realizing an atom chip that enables the integration of laser cooling and trapping into a compact apparatus. Our source delivers ten thousand times more atoms than previous magneto-optical traps with microfabricated optics and, for the first time, can reach sub-Doppler temperatures. Moreover, the same chip design offers a simple way to form stable optical lattices. These features, combined with simplicity of fabrication and ease of operation, make these new traps a key advance in the development of cold-atom technology for high-accuracy, portable measurement devices
Evanescent light-matter Interactions in Atomic Cladding Wave Guides
Alkali vapors, and in particular rubidium, are being used extensively in
several important fields of research such as slow and stored light non-linear
optics3 and quantum computation. Additionally, the technology of alkali vapors
plays a major role in realizing myriad industrial applications including for
example atomic clocks magentometers8 and optical frequency stabilization.
Lately, there is a growing effort towards miniaturizing traditional
centimeter-size alkali vapor cells. Owing to the significant reduction in
device dimensions, light matter interactions are greatly enhanced, enabling new
functionalities due to the low power threshold needed for non-linear
interactions. Here, taking advantage of the mature Complimentary
Metal-Oxide-Semiconductor (CMOS) compatible platform of silicon photonics, we
construct an efficient and flexible platform for tailored light vapor
interactions on a chip. Specifically, we demonstrate light matter interactions
in an atomic cladding wave guide (ACWG), consisting of CMOS compatible silicon
nitride nano wave-guide core with a Rubidium (Rb) vapor cladding. We observe
the highly efficient interaction of the electromagnetic guided mode with the
thermal Rb cladding. The nature of such interactions is explained by a model
which predicts the transmission spectrum of the system taking into account
Doppler and transit time broadening. We show, that due to the high confinement
of the optical mode (with a mode area of 0.3{\lambda}2), the Rb absorption
saturates at powers in the nW regime.Comment: 10 Pages 4 Figures. 1 Supplementar
An integrated atom-photon junction
Photonic chips that integrate guides, switches, gratings and other
components, process vast amounts of information rapidly on a single device. A
new branch of this technology becomes possible if the light is coupled to cold
atoms in a junction of small enough cross section, so that small numbers of
photons interact appreciably with the atoms. Cold atoms are among the most
sensitive of metrological tools and their quantum nature also provides a basis
for new information processing methods. Here we demonstrate a photonic chip
which provides multiple microscopic junctions between atoms and photons. We use
the absorption of light at a junction to reveal the presence of one atom on
average. Conversely, we use the atoms to probe the intensity and polarisation
of the light. Our device paves the way for a new type of chip with
interconnected circuits of atoms and photons.Comment: 5 pages, 4 figure. Submitted to Nature Photonic
High contrast D line electromagnetically induced transparency in nanometric-thin rubidium vapor cell
Electromagnetically induced transparency (EIT) on atomic D line of
rubidium is studied using a nanometric-thin cell with atomic vapor column
length in the range of L= 400 - 800 nm. It is shown that the reduction of the
cell thickness by 4 orders as compared with an ordinary cm-size cell still
allows to form an EIT resonance for ( nm) with the
contrast of up to 40%. Remarkable distinctions of EIT formation in
nanometric-thin and ordinary cells are demonstrated. Despite the Dicke effect
of strong spectral narrowing and increase of the absorption for , EIT resonance is observed both in the absorption and the fluorescence
spectra for relatively low intensity of the coupling laser. Well resolved
splitting of the EIT resonance in moderate magnetic field for
can be used for magnetometry with nanometric spatial resolution. The presented
theoretical model well describes the observed results.Comment: Submitted to Applied Physics B: Lasers and Optics, 9 pages, 10
figure
An Improved Neutron Electric Dipole Moment Experiment
A new measurement of the neutron EDM, using Ramsey's method of separated
oscillatory fields, is in preparation at the new high intensity source of
ultra-cold neutrons (UCN) at the Paul Scherrer Institute, Villigen, Switzerland
(PSI). The existence of a non-zero nEDM would violate both parity and time
reversal symmetry and, given the CPT theorem, might lead to a discovery of new
CP violating mechanisms. Already the current upper limit for the nEDM
(|d_n|<2.9E-26 e.cm) constrains some extensions of the Standard Model.
The new experiment aims at a two orders of magnitude reduction of the
experimental uncertainty, to be achieved mainly by (1) the higher UCN flux
provided by the new PSI source, (2) better magnetic field control with improved
magnetometry and (3) a double chamber configuration with opposite electric
field directions.
The first stage of the experiment will use an upgrade of the RAL/Sussex/ILL
group's apparatus (which has produced the current best result) moved from
Institut Laue-Langevin to PSI. The final accuracy will be achieved in a further
step with a new spectrometer, presently in the design phase.Comment: Flavor Physics & CP Violation Conference, Taipei, 200
Human interleukin-10-related T cell-derived inducible factor: Molecular cloning and functional characterization as an hepatocyte-stimulating factor
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