4,541 research outputs found
Environment-induced decay of teleportation fidelity of the one-qubit state
The one-qubit teleportation protocol is reexamined when it is executed in the
presence of various decohering environments. The results revealed that this
quantum protocol is more robust under the influence of dephaisng environment
than those under the influence of dissipative or noisy environment. The
environment may deprive the quantum advantage of teleportation over purely
classical communication in a finite or infinite lifetime, which is dependent on
the type of environment. Also we found that except entanglement, the purity of
the entangled state resource is also crucial in determine the quality of the
teleported state.Comment: 10 pages, 2 figure
Robustness of Greenberger-Horne-Zeilinger and W states for teleportation in external environments
By solving analytically a master equation in the Lindblad form, we study
quantum teleportation of the one-qubit state under the influence of different
surrounding environments, and compared the robustness between
Greenberger-Horne-Zeilinger (GHZ) and W states in terms of their teleportation
capacity. The results revealed that when subject to zero temperature
environment, the GHZ state is always more robust than the W state, while the
reverse situation occurs when the channel is subject to infinite temperature or
dephasing environment.Comment: 12 pages, 4 figure
Upper bound and shareability of quantum discord based on entropic uncertainty relations
By using the quantum-memory-assisted entropic uncertainty relation (EUR), we
derive a computable tight upper bound for quantum discord, which applies to an
arbitrary bipartite state. Detailed examples show that this upper bound is
tighter than other known bounds in a wide regime. Furthermore, we show that for
any tripartite pure state, the quantum-memory-assisted EUR imposes a constraint
on the shareability of quantum correlations among the constituent parties. This
conclusion amends the well accepted result that quantum discord is not
monogamous.Comment: 5 pages, 1 figure, the final version as that published in Phys. Rev.
Dynamics of entropic measurement-induced nonlocality in structured reservoirs
We propose the entropic measurement-induced nonlocality (MIN) as the maximal
increment of von Neumann entropy induced by the locally non-disturbing
measurement, and study behaviors of it both in the independent and common
structured reservoirs. We present schemes for preserving the MIN, and show that
for certain initial states the MIN, including the quantum correlations, can
even be enhanced by the common reservoir. Additionally, we also show that the
different measures of MIN may give different qualitative characterizations of
nonlocal properties, i.e., it is rather measure dependent than state dependent.Comment: 8 pages, 6 figure
Sudden change of geometric quantum discord in finite temperature reservoirs
We investigate sudden change (SC) behaviors of the distance-based measures of
geometric quantum discords (GQDs) for two non-interacting qubits subject to the
two-sided and the one-sided thermal reservoirs. We found that the GQDs defined
by different distances exhibit different SCs, and thus the SCs are the combined
result of the chosen discord measure and the property of a state. We also found
that the thermal reservoir may generate states having different orderings
related to different GQDs. These inherent differences of the GQDs reveal that
they are incompatible in characterizing quantum correlations both
quantitatively and qualitatively.Comment: 6 pages, 3 figures, the final version as that published in Annals of
Physic
Evolution equation for geometric quantum correlation measures
A simple relation is established for the evolution equation of quantum
information processing protocols such as quantum teleportation, remote state
preparation, Bell-inequality violation and particularly dynamics of the
geometric quantum correlation measures. This relation shows that when the
system traverses the local quantum channel, various figures of merit of the
quantum correlations for different protocols demonstrate a factorization decay
behavior for dynamics. We identified the family of quantum states for different
kinds of quantum channels under the action of which the relation holds. This
relation simplifies the assessment of many quantum tasks.Comment: 7 pages, 2 figure
Evolution equation for quantum coherence
The estimation of the decoherence process of an open quantum system is of
both theoretical significance and experimental appealing. Practically, the
decoherence can be easily estimated if the coherence evolution satisfies some
simple relations. Based on the coherence quantification method, we prove a
simple factorization relation for the norm measure of coherence, and
analyze under which condition this relation holds. We also obtain a more
general relation which applies to arbitrary -qubit state, and determine a
condition for the transformation matrix of the quantum channel which can
support permanently freezing of the norm of coherence. These results
simplify determination of a general decoherence dynamics to that the
investigation of evolution about the representative probe state.Comment: 9 pages (including the Supplemental Material), 1 figure, minor
corrections being mad
Measurement-induced nonlocality based on the trace norm
Nonlocality is one unique property of quantum mechanics differing from
classical world. One of its quantifications can be properly described as the
maximum global effect caused by locally invariant measurements, termed as
measurement-induced nonlocality (MIN) (2011 \emph{Phys. Rev. Lett.} {\bf 106}
120401). Here, we propose to quantify the MIN by the trace norm. We show
explicitly that this measure is monotonically decreasing under the action of
completely positive trace-preserving map, which is the general local quantum
operation, on the unmeasured party for the bipartite state. This property
avoids the undesirable characteristic appearing in the known measure of MIN
defined by the Hilbert-Schmidt norm that may be increased or decreased by
trivial local reversible operations on the unmeasured party. We obtain
analytical formulas of the trace-norm MIN for any dimensional pure
state, two-qubit state, and certain high-dimensional states. As other quantum
correlation measures, the new defined MIN can be directly applied to various
models for physical interpretations.Comment: 6 pages, 1 figure, the final version as that published in New J. Phy
Nonlocal advantage of quantum coherence in high-dimensional states
By local measurements on party of a system and classical
communication between its two parties, one can achieve a nonlocal advantage of
quantum coherence (NAQC) on party . For the norm of coherence and the
relative entropy of coherence, we generalized the framework of NAQC for two
qubits and derived the criteria which capture NAQC in the -dimensional states when is a power of a prime. We also presented a new
framework for formulating NAQC, and showed through explicit examples its
capacity on capturing the NAQC states. Moreover, we proved that any bipartite
state with NAQC is quantum entangled, thus the obtained criteria can also be
used as an entanglement witness.Comment: 5 pages, 2 figures; Final version to be published in Phys. Rev.
Competitions between quantum correlations in the quantum-memory-assisted entropic uncertainty relation
With the aid of a quantum memory, the uncertainty about the measurement
outcomes of two incompatible observables of a quantum system can be reduced. We
investigate this measurement uncertainty bound by considering an additional
quantum system connected with both the quantum memory and the measured quantum
system. We find that the reduction of the uncertainty bound induced by a
quantum memory, on the other hand, implies its increasing for a third
participant. We also show that the properties of the uncertainty bound can be
viewed from perspectives of both quantum and classical correlations, in
particular, the behavior of the uncertainty bound is a result of competitions
of various correlations between different parties.Comment: 5 pages, 2 figures, the final version as that published in Phys. Rev.
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