132 research outputs found
Multipartite quantum correlation and entanglement in four-qubit pure states
Based on the quantitative complementarity relations, we analyze thoroughly
the properties of multipartite quantum correlations and entanglement in
four-qubit pure states. We find that, unlike the three-qubit case, the single
residual correlation, the genuine three- and four-qubit correlations are not
suited to quantify entanglement. More interestingly, from our qualitative and
numerical analysis, it is conjectured that the sum of all the residual
correlations may constitute a good measure for the total multipartite
entanglement in the system.Comment: 7 pages, 3 figue
Multipartite entanglement in four-qubit cluster-class states
Based on quantitative complementarity relations (QCRs), we analyze the
multipartite correlations in four-qubit cluster-class states. It is proven
analytically that the average multipartite correlation is entanglement
monotone. Moreover, it is also shown that the mixed three-tangle is a
correlation measure compatible with the QCRs in this kind of quantum states.
More arrestingly, with the aid of the QCRs, a set of hierarchy entanglement
measures is obtained rigorously in the present system.Comment: 7 pages, 3 figs, version 3, some refs. are adde
Quantum state redistribution based on a generalized decoupling
We develop a simple protocol for a one-shot version of quantum state
redistribution, which is the most general two-terminal source coding problem.
The protocol is simplified from a combination of protocols for the fully
quantum reverse Shannon and fully quantum Slepian-Wolf problems, with its
time-reversal symmetry being apparent. When the protocol is applied to the case
where the redistributed states have a tensor power structure, more natural
resource rates are obtained
Correlation evolution and monogamy of two geometric quantum discords in multipartite systems
We explore two different geometric quantum discords defined respectively via
the trace norm (GQD-1) and Hilbert-Schmidt norm (GQD-2) in multipartite
systems. A rigorous hierarchy relation is revealed for the two GQDs in a class
of symmetric two-qubit -shape states. For multiqubit pure states, it is
found that both GQDs are related to the entanglement concurrence, with the
hierarchy relation being saturated. Furthermore, we look into a four-partite
dynamical system consisting of two cavities interacting with independent
reservoirs. It is found that the GQD-2 can exhibit various sudden change
behaviours, while the GQD-1 only evolves asymptotically, with the two GQDs
exhibiting different monogamous properties.Comment: 5 pages, 3 figure
Detecting a set of entanglement measures in an unknown tripartite quantum state by local operations and classical communication
We propose a more general method for detecting a set of entanglement
measures, i.e. negativities, in an \emph{arbitrary} tripartite quantum state by
local operations and classical communication. To accomplish the detection task
using this method, three observers, Alice, Bob and Charlie, do not need to
perform the partial transposition maps by the structural physical
approximation; instead, they are only required to collectively measure some
functions via three local networks supplemented by a classical communication.
With these functions, they are able to determine the set of negativities
related to the tripartite quantum state.Comment: 16 pages, 2 figures, revte
Exploration of nonlocalities in ensembles consisting of bipartite quantum states
It is revealed that ensembles consisting of multipartite quantum states can
exhibit different kinds of nonlocalities. An operational measure is introduced
to quantify nonlocalities in ensembles consisting of bipartite quantum states.
Various upper and lower bounds for the measure are estimated and the exact
values for ensembles consisting of mutually orthogonal maximally entangled
bipartite states are evaluated.Comment: The title and some contents changed, 4 pages, no figure
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