1,062 research outputs found
Optimized generation of spatial qudits by using a pure phase spatial light modulator
We present a method for preparing arbitrary pure states of spatial qudits,
namely, D-dimensional (D > 2) quantum systems carrying information in the
transverse momentum and position of single photons. For this purpose, a set of
D slits with complex transmission are displayed on a spatial light modulator
(SLM). In a recent work we have shown a method that requires a single
phase-only SLM to control independently the complex coefficients which define
the quantum state of dimension D. The amplitude information was codified by
introducing phase gratings inside each slit and the phase value of the complex
transmission was added to the phase gratings. After a spatial filtering process
we obtained in the image plane the desired qudit state. Although this method
has proven to be a good alternative to compact the previously reported
architectures, it presents some features that could be improved. In this paper
we present an alternative scheme to codify the required phase values that
minimizes the effects of temporal phase fluctuations associated to the SLM
where the codification is carried on. In this scheme the amplitudes are set by
appropriate phase gratings addressed at the SLM while the relative phases are
obtained by a lateral displacement of these phase gratings. We show that this
method improves the quality of the prepared state and provides very high
fidelities of preparation for any state. An additional advantage of this scheme
is that a complete 2\pi modulation is obtained by shifting the grating by one
period, and hence the encoding is not limited by the phase modulation range
achieved by the SLM. Numerical simulations, that take into account the phase
fluctuations, show high fidelities for thousands of qubit states covering the
whole Bloch sphere surface. Similar analysis are performed for qudits with D =
3 and D = 7.Comment: 12 pages, 7 figure
Harmonically Trapped Quantum Gases
We solve the problem of a Bose or Fermi gas in -dimensions trapped by mutually perpendicular harmonic oscillator potentials. From the
grand potential we derive their thermodynamic functions (internal energy,
specific heat, etc.) as well as a generalized density of states. The Bose gas
exhibits Bose-Einstein condensation at a nonzero critical temperature
if and only if , and a jump in the specific heat at if and
only if . Specific heats for both gas types precisely coincide as
functions of temperature when . The trapped system behaves like an
ideal free quantum gas in dimensions. For we recover
all known thermodynamic properties of ideal quantum gases in dimensions,
while in 3D for 1, 2 and 3 one simulates behavior reminiscent of
quantum {\it wells, wires}and{\it dots}, respectively.Comment: 14 pages including 3 figures and 3 table
Improved Quantum Hard-Sphere Ground-State Equations of State
The London ground-state energy formula as a function of number density for a
system of identical boson hard spheres, corrected for the reduced mass of a
pair of particles in a sphere-of-influence picture, and generalized to fermion
hard-sphere systems with two and four intrinsic degrees of freedom, has a
double-pole at the ultimate \textit{regular} (or periodic, e.g.,
face-centered-cubic) close-packing density usually associated with a
crystalline branch. Improved fluid branches are contructed based upon exact,
field-theoretic perturbation-theory low-density expansions for many-boson and
many-fermion systems, appropriately extrapolated to intermediate densities, but
whose ultimate density is irregular or \textit{random} closest close-packing as
suggested in studies of a classical system of hard spheres. Results show
substantially improved agreement with the best available Green-function Monte
Carlo and diffusion Monte Carlo simulations for bosons, as well as with ladder,
variational Fermi hypernetted chain, and so-called L-expansion data for
two-component fermions.Comment: 15 pages and 7 figure
Infinite Matrix Products and the Representation of the Matrix Gamma Function
We introduce infinite matrix products including some of their main properties and convergence results. We apply them in order to extend to the matrix scenario the definition of the scalar gamma function given by an infinite product due to Weierstrass. A limit representation of the matrix gamma function is also provided
Con qué evalúan los estudiantes de Magisterio en formación
Presentamos en este trabajo los instrumentos de evaluación propuestos por estudiantes de
2º curso del Grado de Educación Primaria mientras cursaban la asignatura de Didáctica
de las Ciencias Experimentales en la Universidad de Sevilla. El desarrollo del curso se ha
realizado a partir de una propuesta de enseñanza de las ciencias por investigación escolar,
diseñada en el seno de un Proyecto de I+D+i1. A partir del análisis del contenido de las
tres propuestas de enseñanza que los estudiantes elaboran a lo largo del curso, resulta: 1)
un replanteamiento de la propuesta inicial. 2) diversificación de instrumentos. 3) escaso
uso de instrumentos de evaluación para favorecer la autonomía del estudiante.Ministerio de Ciencia e Innovación EDU2011-2355
Confirmation of symmetrical distributions of clinical attachment loss and tooth loss in a homogeneous Mexican adult male population
Background/purpose
To ascertain whether or not clinical attachment loss and tooth loss are present with similar severity and prevalence across the two sides of the mouth in a homogeneous sample of urban male adults.
Materials and methods
A cross-sectional study was carried out on 161 policemen (a largely homogeneous group in terms of ethnic background, socioeconomic status, sex, occupation, and medical/dental insurance) in Campeche, Mexico. Periodontal examinations were undertaken using the Florida Probe System in a dental chair by one trained and standardized examiner (kappa ≥ 0.60) to determine clinical attachment loss and tooth loss. We examined six sites in all teeth present in the mouth (a maximum of 168 sites, no third molars). Because of correlated data between observations, McNemar (for tooth loss) and Wilcoxon (for attachment loss) signed-rank tests were used to compare right and left sites within the same patient.
Results
The mean age was 38.4 ± 11.0 years. The mean number of teeth present was 24.4 ± 4.6; the mean number of periodontal sites/person was 146.7 ± 27.8. All P values were ≥ 0.05 (except for attachment loss in the upper first premolars), suggesting that there were no statistically significant differences between the right and left sides for the frequency of presentation of these two conditions.
Conclusion
Tooth loss and attachment loss measurements largely resemble each other on both sides of the mouth
Dimensional crossover of a boson gas in multilayers
We obtain the thermodynamic properties for a non-interacting Bose gas
constrained on multilayers modeled by a periodic Kronig-Penney delta potential
in one direction and allowed to be free in the other two directions. We report
Bose-Einstein condensation (BEC) critical temperatures, chemical potential,
internal energy, specific heat, and entropy for different values of a
dimensionless impenetrability between layers. The BEC critical
temperature coincides with the ideal gas BEC critical temperature
when and rapidly goes to zero as increases to infinity for
any finite interlayer separation. The specific heat \textit{vs} for
finite and plane separation exhibits one minimum and one or two maxima
in addition to the BEC, for temperatures larger than which highlights
the effects due to particle confinement. Then we discuss a distinctive
dimensional crossover of the system through the specific heat behavior driven
by the magnitude of . For the crossover is revealed by the change
in the slope of and when , it is evidenced by a broad
minimum in .Comment: Ten pages, nine figure
Maximum-confidence discrimination among symmetric qudit states
We study the maximum-confidence (MC) measurement strategy for discriminating
among nonorthogonal symmetric qudit states. Restricting to linearly dependent
and equally likely pure states, we find the optimal positive operator valued
measure (POVM) that maximizes our confidence in identifying each state in the
set and minimizes the probability of obtaining inconclusive results. The
physical realization of this POVM is completely determined and it is shown that
after an inconclusive outcome, the input states may be mapped into a new set of
equiprobable symmetric states, restricted, however, to a subspace of the
original qudit Hilbert space. By applying the MC measurement again onto this
new set, we can still gain some information about the input states, although
with less confidence than before. This leads us to introduce the concept of
"sequential maximum-confidence" (SMC) measurements, where the optimized MC
strategy is iterated in as many stages as allowed by the input set, until no
further information can be extracted from an inconclusive result. Within each
stage of this measurement our confidence in identifying the input states is the
highest possible, although it decreases from one stage to the next. In
addition, the more stages we accomplish within the maximum allowed, the higher
will be the probability of correct identification. We will discuss an explicit
example of the optimal SMC measurement applied in the discrimination among four
symmetric qutrit states and propose an optical network to implement it.Comment: 14 pages, 4 figures. Published versio
Cancellariidae Gray, 1853 del Plioceno de la provincia de Málaga, España
Se ha realizado un estudio sistemático de la familia Cancellariidae Gray, 1853 del Plioceno de la provincia de Málaga con el objeto de catalogar la malacofauna perteneciente a dicha familia y la consecuente revisión de las categorías taxonómicas supraespecíficas. Se citan 12 especies: una perteneciente a la subfamilia Admetulinae Troschel, 1869: Admetula sp., y 11 pertenecientes a la subfamilia Cancellariinae Gray, 1853: Cancellaria (Bivetiella) cancellata (Linné, 1766); Sveltia lyrata (Brocchi, 1814); Sveltia varricosa (Brocchi, 1814); Calcarata calcarata (Brocchi, 1814); Trigonostoma (Trigonostoma) umbilicaris (Brocchi, 1814); Trigonostoma (Trigonostoma) bellardii (De Stefani & Pantanelli, 1880); Trigonostoma (Ventrilia) cassidea (Brocchi, 1814); Tribia tribulus (Brocchi, 1814); Bonellitia serrata (Bronn, 1831); Bonellitia bonellii (Bellardi, 1841) y Brocchinia mitraeformis (Brocchi, 1814).
Palabras clave: Cancellariidae, Gastropoda, Mollusca, Plioceno, Málaga, España
Monte Carlo Calculations for Liquid He at Negative Pressure
A Quadratic Diffusion Monte Carlo method has been used to obtain the equation
of state of liquid He including the negative pressure region down to the
spinodal point. The atomic interaction used is a renewed version (HFD-B(HE)) of
the Aziz potential, which reproduces quite accurately the features of the
experimental equation of state. The spinodal pressure has been calculated and
the behavior of the sound velociy around the spinodal density has been
analyzed.Comment: 10 pages, RevTex 3.0, with 4 PostScript figures include
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