445 research outputs found
Tripartite entanglement in parametric down-conversion with spatially-structured pump
Most investigations of multipartite entanglement have been concerned with
temporal modes of the electromagnetic field, and have neglected its spatial
structure. We present a simple model which allows to generate tripartite
entanglement between spatial modes by parametric down-conversion with two
symmetrically-tilted plane waves serving as a pump. The characteristics of this
entanglement are investigated. We also discuss the generalization of our scheme
to 2N+1-partite entanglement using 2N symmetrically-tilted plane pump waves.
Another interesting feature is the possibility of entanglement localization in
just two spatial modes.Comment: 6 pages, 2 figure
De scheepsbouwer Panesi: Een geschiedenis van de Oostendse werven en vissersschepen
In 2006 maakte de familie Panesi het bedrijfsarchief en de scheepsplannen in hun bezit over aan het Nationaal Visserijmuseum van Oostduinkerke (navigo). Hoewel de scheepswerf vandaag niet meer bestaat, is Panesi nog prominent aanwezig in de stad. De laatste Oostendse IJslandvaarder O.129 Amandine, die als museumschip aan de Vindictivelaan ligt, is op de Panesiwerf gebouwd. Het gebeurt slechts zelden dat een scheepswerfarchief wordt bewaard. Bij de meeste sluitingen van scheepswerven, zowel aan de kust als in het binnenland, gingen de archieven verloren. De bewaring van dit archief was voor het agentschap Onroerend Erfgoed een uitgelezen kans om te graven in de geschiedenis van de scheepswerf Panesi en, breder, de geschiedenis van de scheepsbouw en het visserijbedrijf in Oostende en aan de kust in de 19de en 20ste eeuw
Laser control for the optimal evolution of pure quantum states
Starting from an initial pure quantum state, we present a strategy for
reaching a target state corresponding to the extremum (maximum or minimum) of a
given observable. We show that a sequence of pulses of moderate intensity,
applied at times when the average of the observable reaches its local or global
extremum, constitutes a strategy transferable to different control issues.
Among them, post-pulse molecular alignment and orientation are presented as
examples. The robustness of such strategies with respect to experimentally
relevant parameters is also examined.Comment: 16 pages, 9 figure
Reaching optimally oriented molecular states by laser kicks
We present a strategy for post-pulse orientation aiming both at efficiency
and maximal duration within a rotational period. We first identify the
optimally oriented states which fulfill both requirements. We show that a
sequence of half-cycle pulses of moderate intensity can be devised for reaching
these target states.Comment: 4 pages, 3 figure
Capacity of a bosonic memory channel with Gauss-Markov noise
We address the classical capacity of a quantum bosonic memory channel with
additive noise, subject to an input energy constraint. The memory is modeled by
correlated noise emerging from a Gauss-Markov process. Under reasonable
assumptions, we show that the optimal modulation results from a "quantum
water-filling" solution above a certain input energy threshold, similar to the
optimal modulation for parallel classical Gaussian channels. We also derive
analytically the optimal multimode input state above this threshold, which
enables us to compute the capacity of this memory channel in the limit of an
infinite number of modes. The method can also be applied to a more general
noise environment which is constructed by a stationary Gauss process. The
extension of our results to the case of broadband bosonic channels with colored
Gaussian noise should also be straightforward.Comment: 11 pages, 4 figures, final corrections mad
Sociodemographic Determinants for Oral Health Risk Profiles
The present study aimed to explore the association between caries risk profiles and different sociodemographic factors .
The study sample (n = 104) was randomly selected within an urban population in Flanders, Belgium. Caries risk was assessed by anamnesis, clinical examination, salivary tests, and a questionnaire. Age, gender, and socio-economic status were extracted from social insurance data files. Social indicators were âoccupational status,â âbeing entitled to the increased allowance for health care interventionsâ and having access to the âMaximum Billâ (MAF), initiatives undertaken to protect deprived families. In the bivariate analysis there were significant differences in risk profiles between occupational groups (P < .001), between entitled and non-entitled individuals to the increased allowance (P = .02), and between access or no-access to the MAF (P < .01). The multiple logistic model showed a significantly higher chance of being in the low risk group for individuals with no-access to the MAF compared to those with access (OR:14.33â95% C.I. 2.14â95.84)
Representation and usage of knowledge for initialization of accelerator control equipment
A knowledge based application, called SETUP, to initialize and diagnose the CERN/PS accelerators' control equipment is described. The object model and the general features of control algorithms are presented, together with their relation to the knowledge description of the setting up of the system. The different ways of the integration of the SETUP in the control system are outlined
Time-dependent unitary perturbation theory for intense laser driven molecular orientation
We apply a time-dependent perturbation theory based on unitary
transformations combined with averaging techniques, on molecular orientation
dynamics by ultrashort pulses. We test the validity and the accuracy of this
approach on LiCl described within a rigid-rotor model and find that it is more
accurate than other approximations. Furthermore, it is shown that a noticeable
orientation can be achieved for experimentally standard short laser pulses of
zero time average. In this case, we determine the dynamically relevant
parameters by using the perturbative propagator, that is derived from this
scheme, and we investigate the temperature effects on the molecular orientation
dynamics.Comment: 16 pages, 6 figure
Properties of Stationary Nonequilibrium States in the Thermostatted Periodic Lorentz Gas II: The many point particles system
We study the stationary nonequilibrium states of N point particles moving
under the influence of an electric field E among fixed obstacles (discs) in a
two dimensional torus. The total kinetic energy of the system is kept constant
through a Gaussian thermostat which produces a velocity dependent mean field
interaction between the particles. The current and the particle distribution
functions are obtained numerically and compared for small E with analytic
solutions of a Boltzmann type equation obtained by treating the collisions with
the obstacles as random independent scatterings. The agreement is surprisingly
good for both small and large N. The latter system in turn agrees with a self
consistent one particle evolution expected to hold in the limit of N going to
infinity.Comment: 14 pages, 9 figure
Non-intersecting squared Bessel paths and multiple orthogonal polynomials for modified Bessel weights
We study a model of non-intersecting squared Bessel processes in the
confluent case: all paths start at time at the same positive value , remain positive, and are conditioned to end at time at . In
the limit , after appropriate rescaling, the paths fill out a
region in the -plane that we describe explicitly. In particular, the paths
initially stay away from the hard edge at , but at a certain critical
time the smallest paths hit the hard edge and from then on are stuck to
it. For we obtain the usual scaling limits from random matrix
theory, namely the sine, Airy, and Bessel kernels. A key fact is that the
positions of the paths at any time constitute a multiple orthogonal
polynomial ensemble, corresponding to a system of two modified Bessel-type
weights. As a consequence, there is a matrix valued
Riemann-Hilbert problem characterizing this model, that we analyze in the large
limit using the Deift-Zhou steepest descent method. There are some novel
ingredients in the Riemann-Hilbert analysis that are of independent interest.Comment: 59 pages, 11 figure
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