21,386 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
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