74 research outputs found
An accelerator mode based technique for studying quantum chaos
We experimentally demonstrate a method for selecting small regions of phase
space for kicked rotor quantum chaos experiments with cold atoms. Our technique
uses quantum accelerator modes to selectively accelerate atomic wavepackets
with localized spatial and momentum distributions. The potential used to create
the accelerator mode and subsequently realize the kicked rotor system is formed
by a set of off-resonant standing wave light pulses. We also propose a method
for testing whether a selected region of phase space exhibits chaotic or
regular behavior using a Ramsey type separated field experiment.Comment: 5 pages, 3 figures, some modest revisions to previous version (esp.
to the figures) to aid clarity; accepted for publication in Physical Review A
(due out on January 1st 2003
Collisional relaxation of Feshbach molecules and three-body recombination in 87Rb Bose-Einstein condensates
We predict the resonance enhanced magnetic field dependence of atom-dimer
relaxation and three-body recombination rates in a Rb Bose-Einstein
condensate (BEC) close to 1007 G. Our exact treatments of three-particle
scattering explicitly include the dependence of the interactions on the atomic
Zeeman levels. The Feshbach resonance distorts the entire diatomic energy
spectrum causing interferences in both loss phenomena. Our two independent
experiments confirm the predicted recombination loss over a range of rate
constants that spans four orders of magnitude.Comment: 4 pages, 3 eps figures (updated references
Planck's scale dissipative effects in atom interferometry
Atom interferometers can be used to study phenomena leading to
irreversibility and dissipation, induced by the dynamics of fundamental objects
(strings and branes) at a large mass scale. Using an effective, but physically
consistent description in terms of a master equation of Lindblad form, the
modifications of the interferometric pattern induced by the new phenomena are
analyzed in detail. We find that present experimental devices can in principle
provide stringent bounds on the new effects.Comment: 12 pages, plain-Te
Analysis of atomic-clock data to constrain variations of fundamental constants
We present a new framework to study the time variation of fundamental
constants in a model-independent way. Model independence implies more free
parameters than assumed in previous studies. Using data from atomic clocks
based on Sr, Yb and Cs, we set bounds on parameters
controlling the variation of the fine-structure constant, , and the
electron-to-proton mass ratio, . We consider variations on timescales
ranging from a minute to almost a day. In addition, we use our results to
derive some of the tightest limits to date on the parameter space of models of
ultralight dark matter and axion-like particles
Quantum resonances and decoherence for delta-kicked atoms
The quantum resonances occurring with delta-kicked atoms when the kicking
period is an integer multiple of the half-Talbot time are analyzed in detail.
Exact results about the momentum distribution at exact resonance are
established, both in the case of totally coherent dynamics and in the case when
decoherence is induced by Spontaneous Emission. A description of the dynamics
when the kicking period is close to, but not exactly at resonance, is derived
by means of a quasi-classical approximation where the detuning from exact
resonance plays the role of the Planck constant. In this way scaling laws
describing the shape of the resonant peaks are obtained. Such analytical
results are supported by extensive numerical simulations, and explain some
recent surprising experimental observations.Comment: 51 pages, 13 figures; KEYWORDS: quantum chaos, decoherence, kicked
rotor, dynamical localization, atom optics; submitted to Nonlinearit
QSNET, a network of clocks for measuring the stability of fundamental constants
The QSNET consortium is building a UK network of next-generation atomic and molecular clocks that will achieve unprecedented sensitivity in testing variations of the fine structure constant, α, and the electron-to-proton mass ratio, μ. This in turn will provide more stringent constraints on a wide range of fundamental and phenomenological theories beyond the Standard Model and on dark matter models
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