7,998 research outputs found
Renormalization of trace distance and multipartite entanglement close to the quantum phase transitions of one- and two-dimensional spin-chain systems
We investigate the quantum phase transitions of spin systems in one and two
dimensions by employing trace distance and multipartite entanglement along with
real-space quantum renormalization group method. As illustration examples, a
one-dimensional and a two-dimensional models are considered. It is shown
that the quantum phase transitions of these spin-chain systems can be revealed
by the singular behaviors of the first derivatives of renormalized trace
distance and multipartite entanglement in the thermodynamics limit. Moreover,
we find the renormalized trace distance and multipartite entanglement obey
certain universal exponential-type scaling laws in the vicinity of the quantum
critical points
Optimal entanglement generation in cavity QED with dissipation
We investigate a two-level atom coupled to a cavity with a strong classical
driving field in a dissipative environment and find an analytical expression of
the time evolution density matrix for the system. The analytical density
operator is then used to study the entanglement between the atom and cavity by
considering the competing process between the atom-field interactions and the
field-environment interactions. It is shown that there is an optimal
interaction time for generating atom-cavity entanglement.Comment: 9 pages, 7 figure
Diffusion and entanglement of a kicked particle in an infinite square well under frequent measurements
We investigate the dynamics of a kicked particle in an infinite square well
undergoing frequent measurements of energy. For a large class of periodic
kicking force, constant diffusion is found in such a non-KAM system. The
influence of phase shift of the kicking potential on the short-time dynamical
behavior is discussed. The general asymptotical measurement-assisted diffusion
rate is obtained. The entanglement between the particle and the measuring
apparatus is investigated. There exist two distinct dynamical behaviors of
entanglement. The bipartite entanglement grows with the kicking steps and it
gains larger value for the more chaotic system. However, the pairwise
entanglement between the system of interest and the partial spins of the
measuring apparatus decreases with the kicking steps. The relation between the
entanglement and quantum diffusion is also analyzed.
PACS numbers: 05.45.Mt, 03.65.TaComment: 7 pages, 5 figures, RevTex4, Accepted by Phys. Rev.
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