1,195 research outputs found
Microfluidic Transport Driven by Opto-Thermal Effects
This chapter reviews several approaches towards the manipulation and transport of fluids and macromolecules by optically-induced thermal effects
A quantum trampoline for ultra-cold atoms
We have observed the interferometric suspension of a free-falling
Bose-Einstein condensate periodically submitted to multiple-order diffraction
by a vertical 1D standing wave. The various diffracted matter waves recombine
coherently, resulting in high contrast interference in the number of atoms
detected at constant height. For long suspension times, multiple-wave
interference is revealed through a sharpening of the fringes. We use this
scheme to measure the acceleration of gravity
Procédé de fabrication de Gaz Naturel de Synthèse par couplage d'une méthanation avec une électrolyse de vapeur d'eau à haute température
National audienceLe procédé présenté ici est un procédé de type Power-to-Gas dont l'objectif est de produire un gaz de synthèse injectable sur les réseaux de gaz naturel, en couplant une électrolyse de vapeur d'eau à haute température à cellule à oxyde solide (Solid Oxide Electrolysis Cell) et une hydrogénation de CO2 afin de produire du méthane, composant majeur du gaz naturel de synthèse. La simulation de ce procédé est réalisée avec le logiciel de simulation ProSim Plus 3® et des modèles spécifiquement développés pour l'électrolyseur à haute température d'une part et pour le réacteur de méthanation d'autre part ont été mis en place. Ces modèles permettent également l'évaluation économique puisque le calcul d'un paramètre de dimensionnement de ces réacteurs est intégré. La simulation, lors de la génération du gaz de synthèse, montre un rendement énergétique élevé (79,2%), supérieur au rendement des filières à basse température. Le procédé développé pour le stockage est également utilisable pour régénérer de l'électricité par réaction électrochimique à partir de gaz naturel
Optical flow focusing: Light-induced destabilization of stable liquid threads
International audienceConfinement of flowing liquid threads by solid walls makes them stable with respect to the Rayleigh–Plateau instability. We demonstrate here that light can break this stability, by forcing locally the deformation of the liquid interface through thermally-induced Marangoni stresses. Depending upon the confining conditions and fluid properties, this optocapillary deformation either pinches or inflates the thread, which may in both cases lead to its localized fragmentation into droplets. In the pinching regime, the laser beam behaves as a wall-free constriction that flow fo-cuses the thread, leading to successive regimes of single and multiple periodicity. Light-driven local Marangoni stresses may prove an elegant contactless alternative to control reversibly the thread-to-droplet transition for digital microfluidics
Sub-Poissonian statistics of Rydberg-interacting dark-state polaritons
Interfacing light and matter at the quantum level is at the heart of modern
atomic and optical physics and enables new quantum technologies involving the
manipulation of single photons and atoms. A prototypical atom-light interface
is electromagnetically induced transparency, in which quantum interference
gives rise to hybrid states of photons and atoms called dark-state polaritons.
We have observed individual dark-state polaritons as they propagate through an
ultracold atomic gas involving Rydberg states. Strong long-range interactions
between Rydberg atoms give rise to an effective interaction blockade for
dark-state polaritons, which results in large optical nonlinearities and
modified polariton number statistics. The observed statistical fluctuations
drop well below the quantum noise limit indicating that photon correlations
modified by the strong interactions have a significant back-action on the
Rydberg atom statistics.Comment: 7 pages, 4 figure
Anisotropic 2D diffusive expansion of ultra-cold atoms in a disordered potential
We study the horizontal expansion of vertically confined ultra-cold atoms in
the presence of disorder. Vertical confinement allows us to realize a situation
with a few coupled harmonic oscillator quantum states. The disordered potential
is created by an optical speckle at an angle of 30{\deg} with respect to the
horizontal plane, resulting in an effective anisotropy of the correlation
lengths of a factor of 2 in that plane. We observe diffusion leading to
non-Gaussian density profiles. Diffusion coefficients, extracted from the
experimental results, show anisotropy and strong energy dependence, in
agreement with numerical calculations
An experimental approach for investigating many-body phenomena in Rydberg-interacting quantum systems
Recent developments in the study of ultracold Rydberg gases demand an
advanced level of experimental sophistication, in which high atomic and optical
densities must be combined with excellent control of external fields and
sensitive Rydberg atom detection. We describe a tailored experimental system
used to produce and study Rydberg-interacting atoms excited from dense
ultracold atomic gases. The experiment has been optimized for fast duty cycles
using a high flux cold atom source and a three beam optical dipole trap. The
latter enables tuning of the atomic density and temperature over several orders
of magnitude, all the way to the Bose-Einstein condensation transition. An
electrode structure surrounding the atoms allows for precise control over
electric fields and single-particle sensitive field ionization detection of
Rydberg atoms. We review two experiments which highlight the influence of
strong Rydberg--Rydberg interactions on different many-body systems. First, the
Rydberg blockade effect is used to pre-structure an atomic gas prior to its
spontaneous evolution into an ultracold plasma. Second, hybrid states of
photons and atoms called dark-state polaritons are studied. By looking at the
statistical distribution of Rydberg excited atoms we reveal correlations
between dark-state polaritons. These experiments will ultimately provide a
deeper understanding of many-body phenomena in strongly-interacting regimes,
including the study of strongly-coupled plasmas and interfaces between atoms
and light at the quantum level.Comment: 14 pages, 11 figures; submitted to a special issue of 'Frontiers of
Physics' dedicated to 'Quantum Foundation and Technology: Frontiers and
Future
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