43 research outputs found
Optical Production of Stable Ultracold Sr Molecules
We have produced large samples of ultracold Sr molecules in the
electronic ground state in an optical lattice. The molecules are bound by 0.05
cm and are stable for several milliseconds. The fast, all-optical method
of molecule creation via intercombination line photoassociation relies on a
near-unity Franck-Condon factor. The detection uses a weakly bound vibrational
level corresponding to a very large dimer. This is the first of two steps
needed to create Sr in the absolute ground quantum state. Lattice-trapped
Sr is of interest to frequency metrology and ultracold chemistry.Comment: 5 pages, 3 figure
Squeezing and entangling nuclear spins in helium 3
We present a realistic model for transferring the squeezing or the
entanglement of optical field modes to the collective ground state nuclear spin
of He using metastability exchange collisions. We discuss in detail the
requirements for obtaining good quantum state transfer efficiency and study the
possibility to readout the nuclear spin state optically
Transport of Atom Packets in a Train of Ioffe-Pritchard Traps
We demonstrate transport and evaporative cooling of several atomic clouds in
a chain of magnetic Ioffe-Pritchard traps moving at a low speed (~m/s). The
trapping scheme relies on the use of a magnetic guide for transverse
confinement and of magnets fixed on a conveyor belt for longitudinal trapping.
This experiment introduces a new approach for parallelizing the production of
Bose-Einstein condensates as well as for the realization of a continuous atom
laser
A quasi-monomode guided atom-laser from an all-optical Bose-Einstein condensate
We report the achievement of an optically guided and quasi-monomode atom
laser, in all spin projection states ( -1, 0 and ) of F=1 in
Rubidium 87. The atom laser source is a Bose-Einstein condensate (BEC) in a
crossed dipole trap, purified to any one spin projection state by a
spin-distillation process applied during the evaporation to BEC. The atom laser
is outcoupled by an inhomogenous magnetic field, applied along the waveguide
axis. The mean excitation number in the transverse modes is for and for the low field seeker
Optimal transport of ultracold atoms in the non-adiabatic regime
We report the transport of ultracold atoms with optical tweezers in the
non-adiabatic regime, i.e. on a time scale on the order of the oscillation
period. We have found a set of discrete transport durations for which the
transport is not accompanied by any excitation of the centre of mass of the
cloud. We show that the residual amplitude of oscillation of the dipole mode is
given by the Fourier transform of the velocity profile imposed to the trap for
the transport. This formalism leads to a simple interpretation of our data and
simple methods for optimizing trapped particles displacement in the
non-adiabatic regime
Evaporative Cooling of a Guided Rubidium Atomic Beam
We report on our recent progress in the manipulation and cooling of a
magnetically guided, high flux beam of atoms. Typically
atoms per second propagate in a magnetic guide providing a
transverse gradient of 800 G/cm, with a temperature K, at an
initial velocity of 90 cm/s. The atoms are subsequently slowed down to cm/s using an upward slope. The relatively high collision rate (5 s)
allows us to start forced evaporative cooling of the beam, leading to a
reduction of the beam temperature by a factor of ~4, and a ten-fold increase of
the on-axis phase-space density.Comment: 10 pages, 8 figure
Long-lived quantum memory with nuclear atomic spins
We propose to store non-classical states of light into the macroscopic
collective nuclear spin ( atoms) of a He vapor, using
metastability exchange collisions. These collisions, commonly used to transfer
orientation from the metastable state to the ground state state of
He, can also transfer quantum correlations. This gives a possible
experimental scheme to map a squeezed vacuum field state onto a nuclear spin
state with very long storage times (hours).Comment: 4 page
Incidencia de bajas dosis de N, P Y S sobre el rendimiento de cebolla Valenciana (Variedad sintética 14)
During the growing season of 1988/89 a trial was held in the large vegetable experimental field at the Agronomy Faculty of the University of La Pampa, under square latin design 5 x 5. Fertilizers of N, P and S were applied to the Synthetical Variety 14 of Valenciana onion. The main objective was to determine the influence of N and its interaction of P and S upon final yield. The fertilizars were: Urea; H(NH4)2 PO4 + Urea; (NH4)2 SO4 +Urea; (NH4)2 SO4 +H(NH4)2 PO4 +Urea and tester. All doses were adjust in such manner all plots had the same amount on N, in order to compare its effects. Highly significantive differences were observed between treatments. With respect to entire plant's weight expose to the air, T2 overcame significantly to Tc and T1. Calcium, Magnesium, phosphorus, crude protein and water contens were analyzed in lab and the results are considered normal. According to the results obtained in the current trial, it might be suggested to fertilize onion with compounds including N and Pinto their composition.En el ciclo 1988/89 se realizĂł en la Huerta Experimental de la Fac. de Agron. de la UNLPam, un ensayo en cuadrado latino 5 x 5, de aplicaci6n de fertilizantes con N, P Y S, en cultivo de "cebollas" variedad sintĂ©tica 14. El objetivo fue constatar la incidencia del N y su interacciĂłn con el P y S sobre el rendimiento del cultivo. Los fertilizantes empleados fueron: Urea; H (NH4)2 PO4 +Urea; (NH4) 2 SO4 +Urea; (NH4) SO4 +H(NH4)2 PO4 +Urea y testigo. En todos los casos las dosis se ajustaron de tal manera que, todas las parcelas en que se aplicaron fertilizantes, vieran la misma cantidad de N para poder comparar sus efectos. En cuanto a los rendimientos de los tratamientos si se observaron diferencias significativas". Respecto al peso planta entera oreada, T2 superĂł significativamente a TO y T1. TambiĂ©n se analizĂł en laboratorio al contenido de calcio, magnesio, fĂłsforo, proteĂna cruda y agua siendo sus valores normales. Sobre la base de los resultados obtenidos en el presente ensayo se aconsejarĂa fertilizar la cebolla con compuestos que tengan N y P en su composiciĂłn
Nonlinear atom interferometer surpasses classical precision limit
Interference is fundamental to wave dynamics and quantum mechanics. The
quantum wave properties of particles are exploited in metrology using atom
interferometers, allowing for high-precision inertia measurements [1, 2].
Furthermore, the state-of-the-art time standard is based on an interferometric
technique known as Ramsey spectroscopy. However, the precision of an
interferometer is limited by classical statistics owing to the finite number of
atoms used to deduce the quantity of interest [3]. Here we show experimentally
that the classical precision limit can be surpassed using nonlinear atom
interferometry with a Bose-Einstein condensate. Controlled interactions between
the atoms lead to non-classical entangled states within the interferometer;
this represents an alternative approach to the use of non-classical input
states [4-8]. Extending quantum interferometry [9] to the regime of large atom
number, we find that phase sensitivity is enhanced by 15 per cent relative to
that in an ideal classical measurement. Our nonlinear atomic beam splitter
follows the "one-axis-twisting" scheme [10] and implements interaction control
using a narrow Feshbach resonance. We perform noise tomography of the quantum
state within the interferometer and detect coherent spin squeezing with a
squeezing factor of -8.2dB [11-15]. The results provide information on the
many-particle quantum state, and imply the entanglement of 170 atoms [16]
Squeezing and entanglement in a Bose-Einstein condensate
Entanglement, a key feature of quantum mechanics, is a resource that allows
the improvement of precision measurements beyond the conventional bound
reachable by classical means. This is known as the standard quantum limit,
already defining the accuracy of the best available sensors for various
quantities such as time or position. Many of these sensors are interferometers
in which the standard quantum limit can be overcome by feeding their two input
ports with quantum-entangled states, in particular spin squeezed states. For
atomic interferometers, Bose-Einstein condensates of ultracold atoms are
considered good candidates to provide such states involving a large number of
particles. In this letter, we demonstrate their experimental realization by
splitting a condensate in a few parts using a lattice potential. Site resolved
detection of the atoms allows the measurement of the conjugated variables atom
number difference and relative phase. The observed fluctuations imply
entanglement between the particles, a resource that would allow a precision
gain of 3.8 dB over the standard quantum limit for interferometric
measurements