1,464 research outputs found
Operational multipartite entanglement classes for symmetric photonic qubit states
We present experimental schemes that allow to study the entanglement classes
of all symmetric states in multiqubit photonic systems. In addition to
comparing the presented schemes in efficiency, we will highlight the relation
between the entanglement properties of symmetric Dicke states and a recently
proposed entanglement scheme for atoms. In analogy to the latter, we obtain a
one-to-one correspondence between well-defined sets of experimental parameters
and multiqubit entanglement classes inside the symmetric subspace of the
photonic system.Comment: 5 pages, 1 figur
Improved orbiter waste collection system study
Design concepts for improved fecal waste collection both on the space shuttle orbiter and as a precursor for the space station are discussed. Inflight usage problems associated with the existing orbiter waste collection subsystem are considered. A basis was sought for the selection of an optimum waste collection system concept which may ultimately result in the development of an orbiter flight test article for concept verification and subsequent production of new flight hardware. Two concepts were selected for orbiter and are shown in detail. Additionally, one concept selected for application to the space station is presented
Vibration isolation mounting system
A system is disclosed for mounting a vibration producing device onto a spacecraft structure and also for isolating the vibration forces thereof from the structure. The system includes a mount on which the device is securely mounted and inner and outer rings. The rings and mount are concentrically positioned. The system includes a base (secured to the structure) and a set of links which are interconnected by a set of torsion bars which allow and resist relative rotational movement therebetween. The set of links are also rotatably connected to a set of brackets which are rigidly connected to the outer ring. Damped leaf springs interconnect the inner and outer rings and the mount allow relative translational movement therebetween in X and Y directions. The links, brackets and base are interconnected and configured so that they allow and resist translational movement of the device in the Z direction so that in combination with the springs they provide absorption of vibrational energy produced by the device in all three dimensions while providing rotational stiffness about all three axes to prevent undesired rotational motions
1s2s2p23d 6L - 1s2p33d 6D, L=F, D, P Transitions in O IV, F V and Ne VI
We present observations of VUV transitions between doubly excited sextet
states in O IV, F V and Ne VI. Spectra were produced by collisions of an O+
beam with a solid carbon target. We also studied spectra obtained previously of
F V and Ne VI. Some observed lines were assigned to the 1s2s2p23d 6L - 1s2p33d
6D, L=F, D, P electric-dipole transitions, and compared with results of MCHF
(with QED and higher-order corrections) and MCDF calculations. 42 new lines
have been identified. Highly excited sextet states in five-electron ions
provide a new form of energy storage and are possible candidates for VUV and
x-ray lasers.Comment: 11 pages, 12 figure
Isotope shifts and hyperfine structure of the Fe I 372 nm resonance line
We report measurements of the isotope shifts of the Fe I resonance line at 372 nm between all four stable
isotopes Fe, Fe, Fe, and Fe, as well as the
complete hyperfine structure of that line for Fe, the only stable
isotope having a non-zero nuclear spin. The field and specific mass shift
coefficients of the transition have been derived from the data, as well as the
experimental value for the hyperfine structure magnetic dipole coupling
constant of the excited state of the transition in Fe: MHz. The measurements were done by means of Doppler-free
laser saturated-absorption spectroscopy in a Fe-Ar hollow cathode using both
natural and enriched iron samples. The measured isotope shifts and hyperfine
constants are reported with uncertainties at the percent level.Comment: 5 pages, 5 figure
Measure of phonon-number moments and motional quadratures through infinitesimal-time probing of trapped ions
A method for gaining information about the phonon-number moments and the
generalized nonlinear and linear quadratures in the motion of trapped ions (in
particular, position and momentum) is proposed, valid inside and outside the
Lamb-Dicke regime. It is based on the measurement of first time derivatives of
electronic populations, evaluated at the motion-probe interaction time t=0. In
contrast to other state-reconstruction proposals, based on measuring Rabi
oscillations or dispersive interactions, the present scheme can be performed
resonantly at infinitesimal short motion-probe interaction times, remaining
thus insensitive to decoherence processes.Comment: 10 pages. Accepted in JPhys
Inter-layer Hall effect in double quantum wells subject to in-plane magnetic fields
We report on a theoretical study of the transport properties of two coupled
two-dimensional electron systems subject to in-plane magnetic fields. The
charge redistribution in double wells induced by the Lorenz force in crossed
electric and magnetic fields has been studied. We have found that the
redistribution of the charge and the related inter-layer Hall effect originate
in the chirality of diamagnetic currents and give a substantial contribution to
the conductivity.Comment: 7 RevTex pages, 4 figures, appendix added and misprint in Eq. (11)
correcte
Deterministic models of quantum fields
Deterministic dynamical models are discussed which can be described in
quantum mechanical terms. -- In particular, a local quantum field theory is
presented which is a supersymmetric classical model. The Hilbert space approach
of Koopman and von Neumann is used to study the classical evolution of an
ensemble of such systems. Its Liouville operator is decomposed into two
contributions, with positive and negative spectrum, respectively. The unstable
negative part is eliminated by a constraint on physical states, which is
invariant under the Hamiltonian flow. Thus, choosing suitable variables, the
classical Liouville equation becomes a functional Schroedinger equation of a
genuine quantum field theory. -- We briefly mention an U(1) gauge theory with
``varying alpha'' or dilaton coupling where a corresponding quantized theory
emerges in the phase space approach. It is energy-parity symmetric and,
therefore, a prototype of a model in which the cosmological constant is
protected by a symmetry.Comment: 6 pages; synopsis of hep-th/0510267, hep-th/0503069, hep-th/0411176 .
Talk at Constrained Dynamics and Quantum Gravity - QG05, Cala Gonone
(Sardinia, Italy), September 12-16, 2005. To appear in the proceeding
- …