73 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
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
Guidelines for developing optical clocks with fractional frequency uncertainty
There has been tremendous progress in the performance of optical frequency
standards since the first proposals to carry out precision spectroscopy on
trapped, single ions in the 1970s. The estimated fractional frequency
uncertainty of today's leading optical standards is currently in the
range, approximately two orders of magnitude better than that of the best
caesium primary frequency standards. This exceptional accuracy and stability is
resulting in a growing number of research groups developing optical clocks.
While good review papers covering the topic already exist, more practical
guidelines are needed as a complement. The purpose of this document is
therefore to provide technical guidance for researchers starting in the field
of optical clocks. The target audience includes national metrology institutes
(NMIs) wanting to set up optical clocks (or subsystems thereof) and PhD
students and postdocs entering the field. Another potential audience is
academic groups with experience in atomic physics and atom or ion trapping, but
with less experience of time and frequency metrology and optical clock
requirements. These guidelines have arisen from the scope of the EMPIR project
"Optical clocks with uncertainty" (OC18). Therefore, the
examples are from European laboratories even though similar work is carried out
all over the world. The goal of OC18 was to push the development of optical
clocks by improving each of the necessary subsystems: ultrastable lasers,
neutral-atom and single-ion traps, and interrogation techniques. This document
shares the knowledge acquired by the OC18 project consortium and gives
practical guidance on each of these aspects
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