4,045 research outputs found
Entanglement verification with finite data
Suppose an experimentalist wishes to verify that his apparatus produces
entangled quantum states. A finite amount of data cannot conclusively
demonstrate entanglement, so drawing conclusions from real-world data requires
statistical reasoning. We propose a reliable method to quantify the weight of
evidence for (or against) entanglement, based on a likelihood ratio test. Our
method is universal in that it can be applied to any sort of measurements. We
demonstrate the method by applying it to two simulated experiments on two
qubits. The first measures a single entanglement witness, while the second
performs a tomographically complete measurement.Comment: 4 pages, 3 pretty picture
Theory of Coupled Multipole Moments Probed by X-ray Scattering in CeB
A minimal model for multipole orders in CeB shows that degeneracy of the
quadrupole order parameters and strong spin-orbit coupling lead to peculiar
temperature and magnetic-field dependences of the X-ray reflection intensity at
superlattice Bragg points. Furthermore, the intensity depends sensitively on
the surface direction. These theoretical results explain naturally recent X-ray
experiments in phases II and III of CeB. It is predicted that under weak
magnetic field perpendicular to the (111) surface, the reflection intensity
should change non-monotonically as a function of temperature.Comment: 4 pages, 5 figure
Structure of boson systems beyond the mean-field
We investigate systems of identical bosons with the focus on two-body
correlations. We use the hyperspherical adiabatic method and a decomposition of
the wave function in two-body amplitudes. An analytic parametrization is used
for the adiabatic effective radial potential. We discuss the structure of a
condensate for arbitrary scattering length. Stability and time scales for
various decay processes are estimated. The previously predicted Efimov-like
states are found to be very narrow. We discuss the validity conditions and
formal connections between the zero- and finite-range mean-field
approximations, Faddeev-Yakubovskii formulation, Jastrow ansatz, and the
present method. We compare numerical results from present work with mean-field
calculations and discuss qualitatively the connection with measurements.Comment: 26 pages, 6 figures, submitted to J. Phys. B. Ver. 2 is 28 pages with
modified figures and discussion
Metastability and Nucleation for the Blume-Capel Model. Different mechanisms of transition
We study metastability and nucleation for the Blume-Capel model: a
ferromagnetic nearest neighbour two-dimensional lattice system with spin
variables taking values in -1,0,+1. We consider large but finite volume, small
fixed magnetic field h and chemical potential "lambda" in the limit of zero
temperature; we analyze the first excursion from the metastable -1
configuration to the stable +1 configuration. We compute the asymptotic
behaviour of the transition time and describe the typical tube of trajectories
during the transition. We show that, unexpectedly, the mechanism of transition
changes abruptly when the line h=2*lambda is crossed.Comment: 96 pages, 44 tex-figures, 7 postscript figure
Description, characteristics and testing of the NASA airborne radar
Presented here is a description of a coherent radar scattermeter and its associated signal processing hardware, which have been specifically designed to detect microbursts and record their radar characteristics. Radar parameters, signal processing techniques and detection algorithms, all under computer control, combine to sense and process reflectivity, clutter, and microburst data. Also presented is the system's high density, high data rate recording system. This digital system is capable of recording many minutes of the in-phase and quadrature components and corresponding receiver gains of the scattered returns for selected spatial regions, as well as other aircraft and hardware related parameters of interest for post-flight analysis. Information is given in viewgraph form
Calorimetric Study of Propane and Ethylbenzene on Active Surface on Carbon-Based Catalysts
The use of carbon materials instead of (mixed) metal oxides in selective oxidation catalysis could emerge to be of basic interest for the catalysis community. Low dimensional carbon allotropes such as multiwalled carbon nanotubes (CNTs) with high structural homogeneity provide the characteristics of model catalysts with well defined active sites as compared with polyvalent transition metal oxides featuring complex electronic and spin structures. The oxydehydrogenation (ODH) reaction over carbon has been discovered in 1979 by Alkhazov et al.[1] From the mechanistic point of view, quinone groups are believed be the active site. These nucleophilic oxygen species can selectively abstract hydrogen atoms and the formed phenol groups are subsequently reoxidized by O2. We choose the ODH of propane and ethylbenzene (EB) as the model reactions. Propane is widely investigated as a substrate in this reaction and mechanistic models for the reaction sequence over metal oxide catalysts are nu-merously suggested. It is equipped with a high C–H bond strength (410.5 kJ mol-1). In contrary to the alkane, the weak C-H bond in benzylic position (357.3 kJ mol-1) makes the molecule highly reactive for ODH
Nonlinear multi-state tunneling dynamics in a spinor Bose-Einstein condensate
We present an experimental realization of dynamic self-trapping and
non-exponential tunneling in a multi-state system consisting of ultracold
sodium spinor gases confined in moving optical lattices. Taking advantage of
the fact that the tunneling process in the sodium spinor system is resolvable
over a broader dynamic energy scale than previously observed in rubidium scalar
gases, we demonstrate that the tunneling dynamics in the multi-state system
strongly depends on an interaction induced nonlinearity and is influenced by
the spin degree of freedom under certain conditions. We develop a rigorous
multi-state tunneling model to describe the observed dynamics. Combined with
our recent observation of spatially-manipulated spin dynamics, these results
open up prospects for alternative multi-state ramps and state transfer
protocols
Three particles in an external trap: Nature of the complete J=0 spectrum
Three bosonic, spin-polarized atoms in a spherical oscillator potential
constitutes the simplest nontrivial Bose-Einstein condensate (BEC). The present
paper develops the tools needed to understand the nature of the complete J=0
energy spectrum for this prototype system, assuming a sum of two-body
potentials. The resulting spectrum is calculated as a function of the two-body
scattering length a_sc, which documents the evolution of certain many-body
levels that evolve from BEC-type to molecular-type as the scattering length is
decreased. Implications for the behavior of the condensate excited-state
spectrum and for condensate formation and decay are elucidated. The energy
levels evolve smoothly, even through the regime where the number of two-body
bound states N_b increases by 1, and a_{sc} switches from -infinity to
infinity. We point out the possibility of suppressing three-body recombination
by tuning the two-body scattering length to values that are larger than the
size of the condensate ground state. Comparisons with mean-field treatments are
presented
Resonant X-Ray Scattering from CeB
We calculate the resonant x-ray scattering (RXS) spectra near the Ce absorption edge in CeB, on the basis of a microscopic model that the
states of Ce are atomic while the states form an energy band with a
reasonable density of states. In the initial state, we employ an effective
Hamiltonian of Shiina {\it et al}. in the antiferro-quadrupole (AFQ) ordering
phase, while we construct the wave function consistent with the neutron
scattering experiment in the magnetic ground state. In the intermediate state,
we take full account of the intra-atomic Coulomb interaction. Without assuming
any lattice distortion, we obtain sufficient RXS intensities on the AFQ
superlattice spot. We obtain the spectral shape, the temperature and magnetic
field dependences in good agreement with the experiment, thus demonstrating the
mechanism that the intensity is brought about by the modulation of states
through the anisotropic term of the - Coulomb interaction. In the
magnetic ground state, a small pre-edge peak is found by the process. On
the magnetic superlattice spot, we get a finite but considerably small
intensity. The magnetic form factor is briefly discussed.Comment: Latex, 10 pages, 12 figures. To be published in J. Phys. Soc. Jpn.,
Vol.71, No. 7 (2002
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