4,456 research outputs found

    Environment-induced decay of teleportation fidelity of the one-qubit state

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    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

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    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

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    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

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    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

    Evolution equation for geometric quantum correlation measures

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    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

    Sudden change of geometric quantum discord in finite temperature reservoirs

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    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 quantum coherence

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    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 l1l_1 norm measure of coherence, and analyze under which condition this relation holds. We also obtain a more general relation which applies to arbitrary NN-qubit state, and determine a condition for the transformation matrix of the quantum channel which can support permanently freezing of the l1l_1 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

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    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 2Γ—n2\times n 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

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    By local measurements on party AA of a system ABAB and classical communication between its two parties, one can achieve a nonlocal advantage of quantum coherence (NAQC) on party BB. For the l1l_1 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 (dΓ—d)(d\times d)-dimensional states when dd 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

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    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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