129,305 research outputs found
Coherent State Control of Non-Interacting Quantum Entanglement
We exploit a novel approximation scheme to obtain a new and compact formula
for the parameters underlying coherent-state control of the evolution of a pair
of entangled two-level systems. It is appropriate for long times and for
relatively strong external quantum control via coherent state irradiation. We
take account of both discrete-state and continuous-variable degrees of freedom.
The formula predicts the relative heights of entanglement revivals and their
timing and duration.Comment: Published in PRA, 10 pages, 7 figure
Alternative Derivation of the Hu-Paz-Zhang Master Equation for Quantum Brownian Motion
Hu, Paz and Zhang [ B.L. Hu, J.P. Paz and Y. Zhang, Phys. Rev. D {\bf 45}
(1992) 2843] have derived an exact master equation for quantum Brownian motion
in a general environment via path integral techniques. Their master equation
provides a very useful tool to study the decoherence of a quantum system due to
the interaction with its environment. In this paper, we give an alternative and
elementary derivation of the Hu-Paz-Zhang master equation, which involves
tracing the evolution equation for the Wigner function. We also discuss the
master equation in some special cases.Comment: 17 pages, Revte
Sudden Death of Entanglement of Two Jaynes-Cummings Atoms
We investigate entanglement dynamics of two isolated atoms, each in its own
Jaynes-Cummings cavity. We show analytically that initial entanglement has an
interesting subsequent time evolution, including the so-called sudden death
effect.Comment: 3 pages, 3 figure
Chemisorption and reactions on clusters of nickel atoms
The nucleation and growth of metallic clusters on a substantially amorphous substrate are discussed with emphasis on the geometrical and electronic structure of the clusters. Several clusters of different symmetry containing five to nine nickel atoms were studied. It was found that the energy range of primary d-like states is not significantly different from the width of the d-band states in nickel metal, as long as the interatomic distance is comparable to that in the bulk metal. The approach of one or more molecules to the cluster is examined using at the hydrogenation of acetylene and the dehydrogenation of ethylene as examples
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