43 research outputs found
Atom interferometry measurement of the electric polarizability of lithium
Using an atom interferometer, we have measured the static electric
polarizability of Li m atomic units with a 0.66% uncertainty. Our experiment, which
is similar to an experiment done on sodium in 1995 by D. Pritchard and
co-workers, consists in applying an electric field on one of the two
interfering beams and measuring the resulting phase-shift. With respect to D.
Pritchard's experiment, we have made several improvements which are described
in detail in this paper: the capacitor design is such that the electric field
can be calculated analytically; the phase sensitivity of our interferometer is
substantially better, near 16 mrad/; finally our interferometer is
species selective it so that impurities present in our atomic beam (other
alkali atoms or lithium dimers) do not perturb our measurement. The extreme
sensitivity of atom interferometry is well illustrated by our experiment: our
measurement amounts to measuring a slight increase of the atom
velocity when it enters the electric field region and our present
sensitivity is sufficient to detect a variation .Comment: 14 page
Incoherent dynamics in neutron-matter interaction
Coherent and incoherent neutron-matter interaction is studied inside a
recently introduced approach to subdynamics of a macrosystem. The equation
describing the interaction is of the Lindblad type and using the Fermi
pseudopotential we show that the commutator term is an optical potential
leading to well-known relations in neutron optics. The other terms, usually
ignored in optical descriptions and linked to the dynamic structure function of
the medium, give an incoherent contribution to the dynamics, which keeps
diffuse scattering and attenuation of the coherent beam into account, thus
warranting fulfilment of the optical theorem. The relevance of this analysis to
experiments in neutron interferometry is briefly discussed.Comment: 15 pages, revtex, no figures, to appear in Phys. Rev.
Dynamical Semigroup Description of Coherent and Incoherent Particle-Matter Interaction
The meaning of statistical experiments with single microsystems in quantum
mechanics is discussed and a general model in the framework of non-relativistic
quantum field theory is proposed, to describe both coherent and incoherent
interaction of a single microsystem with matter. Compactly developing the
calculations with superoperators, it is shown that the introduction of a time
scale, linked to irreversibility of the reduced dynamics, directly leads to a
dynamical semigroup expressed in terms of quantities typical of scattering
theory. Its generator consists of two terms, the first linked to a coherent
wavelike behaviour, the second related to an interaction having a measuring
character, possibly connected to events the microsystem produces propagating
inside matter. In case these events breed a measurement, an explicit
realization of some concepts of modern quantum mechanics ("effects" and
"operations") arises. The relevance of this description to a recent debate
questioning the validity of ordinary quantum mechanics to account for such
experimental situations as, e.g., neutron-interferometry, is briefly discussed.Comment: 22 pages, latex, no figure
An all-solid-state laser source at 671 nm for cold atom experiments with lithium
We present an all solid-state narrow line-width laser source emitting
output power at delivered in a
diffraction-limited beam. The \linebreak source is based on a
fre-quency-doubled diode-end-linebreak pumped ring laser operating on the
transition in Nd:YVO. By using
periodically-poled po-tassium titanyl phosphate (ppKTP) in an external build-up
cavity, doubling efficiencies of up to 86% are obtained. Tunability of the
source over is accomplished. We demonstrate the suitability of
this robust frequency-stabilized light source for laser cooling of lithium
atoms. Finally a simplified design based on intra-cavity doubling is described
and first results are presented
Proposed antimatter gravity measurement with an antihydrogen beam
The principle of the equivalence of gravitational and inertial mass is one of the cornerstones of general relativity. Considerable efforts have been made and are still being made to verify its validity. A quantum-mechanical formulation of gravity allows for non-Newtonian contributions to the force which might lead to a difference in the gravitational force on matter and antimatter. While it is widely expected that the gravitational interaction of matter and of antimatter should be identical, this assertion has never been tested experimentally. With the production of large amounts of cold antihydrogen at the CERN Antiproton Decelerator, such a test with neutral antimatter atoms has now become feasible. For this purpose, we have proposed to set up the AEGIS experiment at CERN/AD, whose primary goal will be the direct measurement of the Earth's gravitational acceleration on antihydrogen with a classical Moiré deflectometer. © 2007 Elsevier B.V. All rights reserved
The Conley Conjecture and Beyond
This is (mainly) a survey of recent results on the problem of the existence
of infinitely many periodic orbits for Hamiltonian diffeomorphisms and Reeb
flows. We focus on the Conley conjecture, proved for a broad class of closed
symplectic manifolds, asserting that under some natural conditions on the
manifold every Hamiltonian diffeomorphism has infinitely many (simple) periodic
orbits. We discuss in detail the established cases of the conjecture and
related results including an analog of the conjecture for Reeb flows, the cases
where the conjecture is known to fail, the question of the generic existence of
infinitely many periodic orbits, and local geometrical conditions that force
the existence of infinitely many periodic orbits. We also show how a recently
established variant of the Conley conjecture for Reeb flows can be applied to
prove the existence of infinitely many periodic orbits of a low-energy charge
in a non-vanishing magnetic field on a surface other than a sphere.Comment: 34 pages, 1 figur
Quantum Physics Exploring Gravity in the Outer Solar System: The Sagas Project
We summarise the scientific and technological aspects of the SAGAS (Search
for Anomalous Gravitation using Atomic Sensors) project, submitted to ESA in
June 2007 in response to the Cosmic Vision 2015-2025 call for proposals. The
proposed mission aims at flying highly sensitive atomic sensors (optical clock,
cold atom accelerometer, optical link) on a Solar System escape trajectory in
the 2020 to 2030 time-frame. SAGAS has numerous science objectives in
fundamental physics and Solar System science, for example numerous tests of
general relativity and the exploration of the Kuiper belt. The combination of
highly sensitive atomic sensors and of the laser link well adapted for large
distances will allow measurements with unprecedented accuracy and on scales
never reached before. We present the proposed mission in some detail, with
particular emphasis on the science goals and associated measurements.Comment: 39 pages. Submitted in abridged version to Experimental Astronom