12,164 research outputs found
Decoherence of tripartite states - a trapped ion coupled to an optical cavity
We investigate the non-dissipative decoherence of three qubit system obtained
by manipulating the state of a trapped two-level ion coupled to an optical
cavity. Modelling the environment as a set of noninteracting harmonic
oscillators, analytical expressions for the state operator of tripartite
composite system, the probability of generating maximally entangled GHZ state,
and the population inversion have been obtained. The pointer observable is the
energy of the isolated quantum system. Coupling to environment results in
exponential decay of off diagonal matrix elements of the state operator with
time as well as a phase decoherence of the component states.
Numerical calculations to examine the time evolution of GHZ state generation
probability and population inversion for different system environment coupling
strengths are performed. Using negativity as an entanglement measure and linear
entropy as a measure of mixedness, the entanglement dynamics of the tripartite
system in the presence of decoherence is analysed.Comment: Revised version, errors corrected and references added. 12 pages, 6
figures, Presented at ICSSUR May 2005, Besancon, Franc
Frequency up- and down-conversions in two-mode cavity quantum electrodynamics
In this letter we present a scheme for the implementation of frequency up-
and down-conversion operations in two-mode cavity quantum electrodynamics
(QED). This protocol for engineering bilinear two-mode interactions could
enlarge perspectives for quantum information manipulation and also be employed
for fundamental tests of quantum theory in cavity QED. As an application we
show how to generate a two-mode squeezed state in cavity QED (the original
entangled state of Einstein-Podolsky-Rosen)
Bilinear and quadratic Hamiltonians in two-mode cavity quantum electrodynamics
In this work we show how to engineer bilinear and quadratic Hamiltonians in
cavity quantum electrodynamics (QED) through the interaction of a single driven
two-level atom with cavity modes. The validity of the engineered Hamiltonians
is numerically analyzed even considering the effects of both dissipative
mechanisms, the cavity field and the atom. The present scheme can be used, in
both optical and microwave regimes, for quantum state preparation, the
implementation of quantum logical operations, and fundamental tests of quantum
theory.Comment: 11 pages, 3 figure
Diluted antiferromagnet in a ferromagnetic enviroment
The question of robustness of a network under random ``attacks'' is treated
in the framework of critical phenomena. The persistence of spontaneous
magnetization of a ferromagnetic system to the random inclusion of
antiferromagnetic interactions is investigated. After examing the static
properties of the quenched version (in respect to the random antiferromagnetic
interactions) of the model, the persistence of the magnetization is analysed
also in the annealed approximation, and the difference in the results are
discussed
Liteira de paricá, tatajuba e eucalipto em sistemas silvipastoris no MunicĂpio de Paragominas - PA.
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