1,503 research outputs found
Communication Enhancement Through Quantum Coherent Control of Channels in an Indefinite Causal-order Scenario
In quantum Shannon theory, transmission of information is enhanced by quantum
features. Up to very recently, the trajectories of transmission remained fully
classical. Recently, a new paradigm was proposed by playing quantum tricks on
two completely depolarizing quantum channels i.e. using coherent control in
space or time of the two quantum channels. We extend here this control to the
transmission of information through a network of an arbitrary number of
channels with arbitrary individual capacity i.e. information preservation
characteristics in the case of indefinite causal order. We propose a formalism
to assess information transmission in the most general case of channels in
an indefinite causal order scenario yielding the output of such transmission.
Then we explicitly derive the quantum switch output and the associated Holevo
limit of the information transmission for , as a function of all
involved parameters. We find in the case that the transmission of
information for three channels is twice of transmission of the two channel case
when a full superposition of all possible causal orders is used
Alterações na fertilidade dos solos em áreas de produção familiar de mandioca no Território do Alto Sertão de Alagoas.
O Território do Alto Sertão de Alagoas, também conhecido como Xingó, é formado por oito municípios (Água Branca, Canapi, Delmiro Gouveia, Inhapi, Mata Grande, Olho D?Água do Casado, Pariconha e Piranhas). Esse território possui uma população estimada de 167.660 habitantes (IBGE, 2007), faz divisa com os estados de Sergipe, Bahia e Pernambuco, perfazendo uma área de 3.905,4 km2.bitstream/item/122986/1/Alteracoes-na-fertilidade-COT-89-On-line.pd
Continuous-variable entanglement of two bright coherent states that never interacted
We study continuous-variable entanglement of bright quantum states in a pair
of evanescently coupled nonlinear waveguides operating in the
regime of degenerate down-conversion. We consider the case where only the
energy of the nonlinearly generated fields is exchanged between the waveguides
while the pump fields stay independently guided in each original waveguide. We
show that this device, when operated in the depletion regime, entangles the two
non-interacting bright pump modes due to a nonlinear cascade effect. It is also
shown that two-colour quadripartite entanglement can be produced when certain
system parameters are appropriately set. This device works in the
traveling-wave configuration, such that the generated quantum light shows a
broad spectrum. The proposed device can be easily realized with current
technology and therefore stands as a good candidate for a source of bipartite
or multipartite entangled states for the emerging field of optical
continuous-variable quantum information processing.Comment: 10 pages, 12 figure
Attenuation of Lightning-Induced Effects on Overhead Distribution Systems in Urban Areas
Overhead distribution systems can be strongly affected and damaged by indirect lightning. The induced voltages are usually computed neglecting the surrounding geometry and the presence of buildings in urban areas. Buildings can strongly change the behavior of the measured lighting-induced electromagnetic (EM) fields in the proximity of the point of impact. As a consequence, induced voltages can deviate from what would be measured in the absence of buildings. This work proposes an analysis of the main variables, which affect the deviation of the EM fields and of the consequent induced voltages along an overhead distribution line due to the presence of a building. Different distances between the line and the building and different building heights are considered
Coherent control of two Jaynes-Cummings cavities
In this work, we uncover new features on the study of a two-level atom
interacting with one of two cavities in a coherent superposition. The
James-Cummings model is used to describe the atom-field interaction and to
study the effects of quantum indefiniteness on such an interaction. We show
that coherent control of the two cavities in an undefined manner allows novel
possibilities to manipulate the atomic dynamics on demand which are not
achievable in the conventional way. In addition, it is shown that the coherent
control of the atom creates highly entangled states of the cavity fields taking
a Bell-like or Schr\"odinger-cat-like state form. Our results are a step
forward to understand and harness quantum systems in a coherent control, and
open a new research avenue in the study of atom-field interaction exploiting
quantum indefiniteness
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