7,800 research outputs found
The transfer matrix: a geometrical perspective
We present a comprehensive and self-contained discussion of the use of the
transfer matrix to study propagation in one-dimensional lossless systems,
including a variety of examples, such as superlattices, photonic crystals, and
optical resonators. In all these cases, the transfer matrix has the same
algebraic properties as the Lorentz group in a (2+1)-dimensional spacetime, as
well as the group of unimodular real matrices underlying the structure of the
abcd law, which explains many subtle details. We elaborate on the geometrical
interpretation of the transfer-matrix action as a mapping on the unit disk and
apply a simple trace criterion to classify the systems into three types with
very different geometrical and physical properties. This approach is applied to
some practical examples and, in particular, an alternative framework to deal
with periodic (and quasiperiodic) systems is proposed.Comment: 50 pages, 24 figure
Intelligent Packaging Systems: Sensors and Nanosensors to Monitor Food Quality and Safety
Indexación: Web of Science y Scopus.The application of nanotechnology in different areas of food packaging is an emerging field that will grow rapidly in the coming years. Advances in food safety have yielded promising results leading to the development of intelligent packaging (IP). By these containers, it is possible to monitor and provide information of the condition of food, packaging, or the environment. This article describes the role of the different concepts of intelligent packaging. It is possible that this new technology could reach enhancing food safety, improving pathogen detection time, and controlling the quality of food and packaging throughout the supply chain.https://www.hindawi.com/journals/js/2016/4046061/cta
Informational completeness of continuous-variable measurements
We justify that homodyne tomography turns out to be informationally complete
when the number of independent quadrature measurements is equal to the
dimension of the density matrix in the Fock representation. Using this as our
thread, we examine the completeness of other schemes, when continuous-variable
observations are truncated to discrete finite-dimensional subspaces.Comment: To appear in Phys. Rev.
Metastable states influence on the magnetic behavior of the triangular lattice: Application to the spin-chain compound Ca3Co2O6
It is known that the spin-chain compound Ca3Co2O6 exhibits very interesting
plateaus in the magnetization as a function of the magnetic field at low
temperatures. The origin of them is still controversial. In this paper we study
the thermal behavior of this compound with a single-flip Monte Carlo simulation
on a triangular lattice and demonstrate the decisive influence of metastable
states in the splitting of the ferrimagnetic 1/3 plateau below 10 K. We
consider the [Co2O6]n chains as giant magnetic moments described by large Ising
spins on planar clusters with open boundary conditions. With this simple
frozen-moment model we obtain stepped magnetization curves which agree quite
well with the experimental results for different sweeping rates. We describe
particularly the out-of-equilibrium states that split the low-temperature 1/3
plateau into three steps. They relax thermally to the 1/3 plateau, which has
long-range order at the equilibrium. Such states are further analyzed with
snapshots unveiling a domain-wall structure that is responsible for the
observed behavior of the 1/3 plateau. A comparison is also given of the exact
results in small triangular clusters with our Monte Carlo results, providing
further support for our thermal description of this compound.Comment: 8 pages, 11 figures, submitted to PR
Discrete phase-space structure of -qubit mutually unbiased bases
We work out the phase-space structure for a system of qubits. We replace
the field of real numbers that label the axes of the continuous phase space by
the finite field \Gal{2^n} and investigate the geometrical structures
compatible with the notion of unbiasedness. These consist of bundles of
discrete curves intersecting only at the origin and satisfying certain
additional properties. We provide a simple classification of such curves and
study in detail the four- and eight-dimensional cases, analyzing also the
effect of local transformations. In this way, we provide a comprehensive
phase-space approach to the construction of mutually unbiased bases for
qubits.Comment: Title changed. Improved version. Accepted for publication in Annals
of Physic
Pulsed x-rays dose measurements from a hundred joules plasma focus device
Indexación: Scopus.Present work is aimed to perform dosimetric measurements to characterize dosis obtained from pulsed x-rays emitted from a hundred joules plasma focus device PF-400J using thermoluminescent dosimeters (TLD-100). Two dosimeter arrays (containing 21 dosimeters in each) were used. One of the arrays was kept inside the PF-400J vacuum chamber and other outside the vacuum chamber, simultaneously. It was found that dosis obtained from the inside array (∼200.7 mGy) were hundred times larger than the outside array (∼1.1 mGy) for hundred pulses of x-rays. Later, the vacuum window of PF-400J, which was made of 1 mm aluminum, was replaced by a plastic window and a similar dosimeter array was kept outside the chamber over the plastic window. With this arrangement, the obtained doses (100 pulses of x-rays) were of the same order of magnitude (∼106 mGy) as it was inside the vacuum chamber. Later, a lead piece was inserted inside the hollow anode of PF-400J, which increased dose (∼250 mGy) per hundred pulses of x-ray outside the vacuum chamber using plastic vacuum window. Our results suggest that PF-400J could be a useful device to study low dose pulsed radiation effects on cancer cell lines in in vitro experiments. © Published under licence by IOP Publishing Ltd.The work is supported by grant ACT-1115, CONICYT, Chile.https://iopscience.iop.org/article/10.1088/1742-6596/1043/1/01204
Extremal states for photon number and quadratures as gauges for nonclassicality
Rotated quadratures carry the phase-dependent information of the
electromagnetic field, so they are somehow conjugate to the photon number. We
analyze this noncanonical pair, finding an exact uncertatinty relation, as well
as a couple of weaker inequalities obtained by relaxing some restrictions of
the problem. We also find the intelligent states saturating that relation and
complete their characterization by considering extra constraints on the
second-order moments of the variables involved. Using these moments, we
construct performance measures tailored to diagnose photon-added and
Schr\"odinger catlike states, among others.Comment: 6 pages, 4 color figures. Comments welcome
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