11,103 research outputs found
COMPARATIVE STUDY OF DIFFERENT MODELS FOR CALCULATION OF DNI
For prospecting or design of Concentrating Solar Power (CSP) systems it is necessary to know the distribution of the Direct Normal Irradiance (DNI) of the region. However, due to the recurring operational problems of measuring instruments, the use of mathematical models estimating the local DNI can be a very useful tool. The objective of this work is to construct a mathematical model that is used in the calculation of the DNI using experimental data provided by the Laboratory of Tropical Environmental Variables (LAVAT/INPE). This model was compared with other mathematical models already present in the literature. The consideration of clean-sky was used, that is, the effects of cloudiness, among others, were neglected
Normalization procedure for relaxation studies in NMR quantum information processing
NMR quantum information processing studies rely on the reconstruction of the
density matrix representing the so-called pseudo-pure states (PPS). An
initially pure part of a PPS state undergoes unitary and non-unitary
(relaxation) transformations during a computation process, causing a "loss of
purity" until the equilibrium is reached. Besides, upon relaxation, the nuclear
polarization varies in time, a fact which must be taken into account when
comparing density matrices at different instants. Attempting to use time-fixed
normalization procedures when relaxation is present, leads to various anomalies
on matrices populations. On this paper we propose a method which takes into
account the time-dependence of the normalization factor. From a generic form
for the deviation density matrix an expression for the relaxing initial pure
state is deduced. The method is exemplified with an experiment of relaxation of
the concurrence of a pseudo-entangled state, which exhibits the phenomenon of
sudden death, and the relaxation of the Wigner function of a pseudo-cat state.Comment: 9 pages, 5 figures, to appear in QI
Importância da utilização de resÃduos agropecuários na produção de pequenos ruminantes para famÃlias de baixa renda no Nordeste do Brasil
A produção de cana-de-açúcar em nosso paÃs, é de mais de 310 milhões de toneladas da cana-de-açúcar, cultivadas em cerca de quatro milhões de hectares.bitstream/item/123055/1/Importancia-da-utilizacao-de-residuos.pd
Distinct magnetic regimes through site-selective atom substitution in the frustrated quantum antiferromagnet CsCuClBr
We report on a systematic study of the magnetic properties on single crystals
of the solid solution CsCuClBr (0 x 4), which
include the two known end-member compounds CsCuCl and CsCuBr,
classified as quasi-two-dimensional quantum antiferromagnets with different
degrees of magnetic frustration. By comparative measurements of the magnetic
susceptibility () on as many as eighteen different Br concentrations,
we found that the inplane and out-of-plane magnetic correlations, probed by the
position and height of a maximum in the magnetic susceptibility, respectively,
do not show a smooth variation with x. Instead three distinct concentration
regimes can be identified, which are separated by critical concentrations
x = 1 and x = 2. This unusual magnetic behavior can be explained
by considering the structural peculiarities of the materials, especially the
distorted Cu-halide tetrahedra, which support a site-selective replacement of
Cl- by Br- ions. Consequently, the critical concentrations x (x)
mark particularly interesting systems, where one (two) halidesublattice
positions are fully occupied.Comment: 15 pages, 4 figure
Environment-induced sudden transition in quantum discord dynamics
Non-classical correlations play a crucial role in the development of quantum
information science. The recent discovery that non-classical correlations can
be present even in separable (unentangled) states has broadened this scenario.
This generalized quantum correlation has been increasing relevance in several
fields, among them quantum communication, quantum computation, quantum phase
transitions, and biological systems. We demonstrate here the occurrence of the
sudden-change phenomenon and immunity against some sources of noise for the
quantum discord and its classical counterpart, in a room temperature nuclear
magnetic resonance setup. The experiment is performed in a decohering
environment causing loss of phase relations among the energy eigenstates and
exchange of energy between system and environment, resulting in relaxation to a
Gibbs ensemble
Quantum state tomography and quantum logical operations in a three qubits NMR quadrupolar system
In this work, we present an implementation of quantum logic gates and
algorithms in a three effective qubits system, represented by a (I = 7/2) NMR
quadrupolar nuclei. To implement these protocols we have used the strong
modulating pulses (SMP). The various stages of each implementation were
verified by quantum state tomography (QST). It is presented here the results
for the computational base states, Toffolli logic gates, and Deutsch-Jozsa and
Grover algorithms. Also, we discuss the difficulties and advantages of
implementing such protocols using the SMP technique in quadrupolar systems.Comment: 24 pages, 8 figure
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