1,680 research outputs found
Robustness of quantum discord to sudden death
We calculate the dissipative dynamics of two-qubit quantum discord under
Markovian environments. We analyze various dissipative channels such as
dephasing, depolarizing, and generalized amplitude damping, assuming
independent perturbation, in which each qubit is coupled to its own channel.
Choosing initial conditions that manifest the so-called sudden death of
entanglement, we compare the dynamics of entanglement with that of quantum
discord. We show that in all cases where entanglement suddenly disappears,
quantum discord vanishes only in the asymptotic limit, behaving similarly to
individual decoherence of the qubits, even at finite temperatures. Hence,
quantum discord is more robust than the entanglement against to decoherence so
that quantum algorithms based only on quantum discord correlations may be more
robust than those based on entanglement.Comment: 4 figures, 4 page
Purity as a witness for initial system-environment correlations in open-system dynamics
We study the dynamics of a two-level atom interacting with a Lorentzian
structured reservoir considering initial system-environment correlations. It is
shown that under strong system-reservoir coupling the dynamics of purity can
determine whether there are initial correlations between system and
environment. Moreover, we investigate the interaction of two two-level atoms
with the same reservoir. In this case, we show that besides determining if
there are initial system-environment correlations, the dynamics of the purity
of the atomic system allows the identification of the distinct correlated
initial states. In addition, the dynamics of quantum and classical correlations
is analyzed.Comment: 6 pages, 3 figure
Anisotropic diffusion in continuum relaxation of stepped crystal surfaces
We study the continuum limit in 2+1 dimensions of nanoscale anisotropic
diffusion processes on crystal surfaces relaxing to become flat below
roughening. Our main result is a continuum law for the surface flux in terms of
a new continuum-scale tensor mobility. The starting point is the Burton,
Cabrera and Frank (BCF) theory, which offers a discrete scheme for atomic steps
whose motion drives surface evolution. Our derivation is based on the
separation of local space variables into fast and slow. The model includes: (i)
anisotropic diffusion of adsorbed atoms (adatoms) on terraces separating steps;
(ii) diffusion of atoms along step edges; and (iii) attachment-detachment of
atoms at step edges. We derive a parabolic fourth-order, fully nonlinear
partial differential equation (PDE) for the continuum surface height profile.
An ingredient of this PDE is the surface mobility for the adatom flux, which is
a nontrivial extension of the tensor mobility for isotropic terrace diffusion
derived previously by Margetis and Kohn. Approximate, separable solutions of
the PDE are discussed.Comment: 14 pages, 1 figur
Derivation of the Blackbody Radiation Spectrum from a Natural Maximum-Entropy Principle Involving Casimir Energies and Zero-Point Radiation
By numerical calculation, the Planck spectrum with zero-point radiation is
shown to satisfy a natural maximum-entropy principle whereas alternative
choices of spectra do not. Specifically, if we consider a set of
conducting-walled boxes, each with a partition placed at a different location
in the box, so that across the collection of boxes the partitions are uniformly
spaced across the volume, then the Planck spectrum correspond to that spectrum
of random radiation (having constant energy kT per normal mode at low
frequencies and zero-point energy (1/2)hw per normal mode at high frequencies)
which gives maximum uniformity across the collection of boxes for the radiation
energy per box. The analysis involves Casimir energies and zero-point radiation
which do not usually appear in thermodynamic analyses. For simplicity, the
analysis is presented for waves in one space dimension.Comment: 11 page
Utilização do equipamento Photon-citrus para a montagem de classificadores capazes de realizar o diagnóstico de HLB (greening).
Avaliação da utilização da técnica de espectroscopia de fluorescência induzida por laser na detecção de doenças em citros.
Influência do preparo do solo, sistema de plantio e porta-enxerto no crescimento de Laranjeira Pêra em condições geoambientais dos Tabuleiros Costeiros da Bahia.
Na Bahia, 80% da área citrícola encontra-se na Grande Unidade de Paisagem Tabuleiros Costeiros, em propriedades de até dez hectares (agricultura familiar). Objetiva-se um modelo de manejo que possibilite sustentabilidade, menor relação custo/benefício e maior produtividade de pomares cítricos especialmente destinados a essas propriedades.Em paralelo aconteceram também os seguintes eventos: V Seminário de Pesquisa do Recôncavo da Bahia; V Seminário Estudantil de Pesquisa da UFRB; V Seminário da Pós-Graduação da UFRB; II Seminário Regional de Pesquisa da EBDA; 5ª Jornada Científica da Embrapa Mandioca e Fruticultura; VIII Seminário Estudantil de Pesquisa e Extensão da FAMAM; Semana de Ciência, Tecnologia e Inovação no Agronegócio; Fórum de Gestores de Iniciação Científica e Tecnológica da Bahia; II Simpósio Baiano de Defesa Agropecuária; I Semana de Educação Tutorial da UFRB
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