6,058 research outputs found
Atomic Focusing by Quantum Fields: Entanglement Properties
The coherent manipulation of the atomic matter waves is of great interest
both in science and technology. In order to study how an atom optic device
alters the coherence of an atomic beam, we consider the quantum lens proposed
by Averbukh et al [1] to show the discrete nature of the electromagnetic field.
We extend the analysis of this quantum lens to the study of another essentially
quantum property present in the focusing process, i.e., the atom-field
entanglement, and show how the initial atomic coherence and purity are affected
by the entanglement. The dynamics of this process is obtained in closed form.
We calculate the beam quality factor and the trace of the square of the reduced
density matrix as a function of the average photon number in order to analyze
the coherence and purity of the atomic beam during the focusing process.Comment: 10 pages, 4 figure
The quantum brachistochrone problem for non-Hermitian Hamiltonians
Recently Bender, Brody, Jones and Meister found that in the quantum brachistochrone problem the passage time needed for the evolution of certain initial states into specified final states can be made arbitrarily small, when the time-evolution operator is taken to be non-Hermitian but PT-symmetric. Here we demonstrate that such phenomena can also be obtained for non-Hermitian Hamiltonians for which PT-symmetry is completely broken, i.e. dissipative systems. We observe that the effect of a tunable passage time can be achieved by projecting between orthogonal eigenstates by means of a time-evolution operator associated with a non-Hermitian Hamiltonian. It is not essential that this Hamiltonian is PT-symmetric
Sistema de gerenciamento de campos experimentais - SiCamp.
O mapa do campo experimental. Principais funcionalidades do sistema. Resultados parciais e trabalhos futuros.bitstream/item/76636/1/CNPTIA-COM.TEC.-4-99.pd
Thermodynamics of Pseudo-Hermitian Systems in Equilibrium
In study of pseudo(quasi)-hermitian operators, the key role is played by the
positive-definite metric operator. It enables physical interpretation of the
considered systems. In the article, we study the pseudo-hermitian systems with
constant number of particles in equilibrium. We show that the explicit
knowledge of the metric operator is not essential for study of thermodynamic
properties of the system. We introduce a simple example where the physically
relevant quantities are derived without explicit calculation of either metric
operator or spectrum of the Hamiltonian.Comment: 9 pages, 2 figures, to appear in Mod.Phys.Lett. A; historical part of
sec. 2.1 reformulated, references corrected; typos correcte
Existence criteria for stabilization from the scaling behaviour of ionization probabilities
We provide a systematic derivation of the scaling behaviour of various
quantities and establish in particular the scale invariance of the ionization
probability. We discuss the gauge invariance of the scaling properties and the
manner in which they can be exploited as consistency check in explicit
analytical expressions, in perturbation theory, in the Kramers-Henneberger and
Floquet approximation, in upper and lower bound estimates and fully numerical
solutions of the time dependent Schroedinger equation. The scaling invariance
leads to a differential equation which has to be satisfied by the ionization
probability and which yields an alternative criterium for the existence of
atomic bound state stabilization.Comment: 12 pages of Latex, one figur
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