52,125 research outputs found

    Structure of correlated initial states that guarantee completely positive reduced dynamics

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    We use the Koashi-Imoto decomposition of the degrees of freedom of joint system-environment initial states to investigate the reduced dynamics. We show that a subset of joint system-environment initial states guarantees completely positive reduced dynamics, if and only if the system privately owns all quantum degrees of freedom and can locally access the classical degrees of freedom, without disturbing all joint initial states in the given subset. Furthermore, we show that the quantum mutual information for such kinds of states must be independent of the quantum degrees of freedom.Comment: 5 pages, 1 figure. Accepted version. To appear in Physical Review

    Measurements of strong phase in D0KπD^0\to K\pi decay and yCPy_\mathrm{CP} at BESIII

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    In this paper, I report the preliminary results of the strong phase difference cosδKπ\cos\delta_{K\pi} between the doubly Cabibbo-suppressed process D0Kπ+\overline{D}{}^0\to K^- \pi^+ and Cabibbo-favored D0Kπ+D^0\to K^- \pi^+ at BESIII. In addition, the preliminary results of the D0D^0-D0\overline{D}{}^0 mixing parameter yCPy_\mathrm{CP} by analyzing CPCP-tagged semileptonic DD decays are presented. These measurements were carried out based on the quantum-correlated technique in studying the process of D0D0D^0\overline{D}{}^0 pair productions of 2.92 fb1^{-1} e+ee^+e^- collision data collected with the BESIII detector at s\sqrt{s} = 3.773 GeV.Comment: minor change; to appear in the proceedings of The 6th International Workshop on Charm Physics (CHARM 2013

    Recent Progress on Charmonium Decays at BESIII

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    In 2009, the BESIII experiment has collected about 225M \jpsi and 106M \psip samples, both of which are the world largest on-peak charmonium production. Based on these dataset, BESIII has made great effort on the study of the charmonium decays, some important of which have been reviewed in this proceeding. In addition, a searching for new physics through the CP/PCP/P violation process is reported.Comment: 7 pages, 1 figure, Proceeding for 5th International Conference in High-Energy Physics: HEP-MAD 11, 25-31 August 2011, Antananarivo, Madagasca

    Further Results on Existentially Closed Graphs Arising from Block Designs

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    A graph is nn-existentially closed (nn-e.c.) if for any disjoint subsets AA, BB of vertices with AB=n|{A \cup B}|=n, there is a vertex zABz \notin A \cup B adjacent to every vertex of AA and no vertex of BB. For a block design with block set B\cal B, its block intersection graph is the graph whose vertex set is B\cal B and two vertices (blocks) are adjacent if they have non-empty intersection. In this paper, we investigate the block intersection graphs of pairwise balanced designs, and propose a sufficient condition for such graphs to be 22-e.c. In particular, we study the λ\lambda-fold triple systems with λ2\lambda \ge 2 and determine for which parameters their block intersection graphs are 11- or 22-e.c. Moreover, for Steiner quadruple systems, the block intersection graphs and their analogue called {1}\{1\}-block intersection graphs are investigated, and the necessary and sufficient conditions for such graphs to be 22-e.c. are established.Comment: 11 page

    Deforming symplectomorphism of certain irreducible Hermitian symmetric spaces of compact type by mean curvature flow

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    In this paper, we generalize Medos-Wang's arguments and results on the mean curvature flow deformations of symplectomorphisms of \CP^n in \cite{MeWa} to complex Grassmann manifold G(n, n+m;\C) and compact totally geodesic K\"ahler-Einstein submanifolds of G(n, 2n;\C) such as irreducible Hermitian symmetric spaces SO(2n)/U(n)SO(2n)/U(n) and Sp(n)/U(n)Sp(n)/U(n) (in the terminology of \cite[p. 518]{He}). We also give an abstract result and discuss the case of complex tori.Comment: 48 pages:Add a word "certain" in the title: The arguments of improving pinching condition in Theorems 1.1 and 1.2 of the previous version are incorrect: Theorems 1.1 and 1.2 in the present version can only be proved under the same pinching condition as that of the reference [22

    Experimental realization of a fetching algorithm in a 7 qubit NMR quantum computer

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    Searching for marked items from an unsorted database is an important scientific problem and a benchmark for computing devices as well. Using a 7-qubit liquid NMR quantum computer, we have demonstrated successfully an hybrid quantum fetching algorithm that finds marked items using only a single query. The essential idea is the operation of quantum computers in parallel. We gave the detailed pulse sequence for coherent control of the 7 qubits. The pulse sequence demonstrated here is not only useful for ensemble quantum computation, but also can be regarded as a general purpose control-gate which is useful for experimental design of quantum algorithms and general quantum information processing task in other quantum computer schemes. A generalization of the algorithm that is scalable to arbitrary qubit number is also provided.Comment: 13 pages, 3 figures. Comments and criticism are welcom

    Quantum Weiss-Weinstein bounds for quantum metrology

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    Sensing and imaging are among the most important applications of quantum information science. To investigate their fundamental limits and the possibility of quantum enhancements, researchers have for decades relied on the quantum Cram\'er-Rao lower error bounds pioneered by Helstrom. Recent work, however, has called into question the tightness of those bounds for highly nonclassical states in the non-asymptotic regime, and better methods are now needed to assess the attainable quantum limits in reality. Here we propose a new class of quantum bounds called quantum Weiss-Weinstein bounds, which include Cram\'er-Rao-type inequalities as special cases but can also be significantly tighter to the attainable error. We demonstrate the superiority of our bounds through the derivation of a Heisenberg limit and phase-estimation examples.Comment: 7 pages, 2 figures, accepted by Quantum Science and Technolog

    Gorenstein homological properties of tensor rings

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    Let RR be a two-sided noetherian ring and MM be a nilpotent RR-bimodule, which is finitely generated on both sides. We study Gorenstein homological properties of the tensor ring TR(M)T_R(M). Under certain conditions, the ring RR is Gorenstein if and only if so is TR(M)T_R(M). We characterize Gorenstein projective TR(M)T_R(M)-modules in terms of RR-modules

    Payoff Allocation of Service Coalition in Wireless Mesh Network: A Cooperative Game Perspective

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    In wireless mesh network (WMN), multiple service providers (SPs) can cooperate to share resources (e.g., relay nodes and spectrum), to serve their collective subscribed customers for better service. As a reward, SPs are able to achieve more individual benefits, i.e., increased revenue or decreased cost, through efficient utilization of shared network resources. However, this cooperation can be realized only if fair allocation of aggregated payoff, which is the sum of the payoff of all the cooperative SPs, can be achieved. We first formulate such cooperation as a coalitional game with transferable utility, specifically, a linear programming game, in which, each SP should obtain the fair share of the aggregated payoff. Then we study the problem of allocating aggregated payoff which leads to stable service coalition of SPs in WMN based on the concepts of dual payoff and Shapley value.Comment: IEEE GlobeCom. 6 pages, 6 figures, 1 tabl

    A Layered Coalitional Game Framework of Wireless Relay Network

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    A wireless relay network (WRN) has recently emerged as an effective way to increase communication capacity and extend a coverage area with a low cost. In the WRN, multiple service providers (SPs) can cooperate to share their resources (e.g., relay nodes and spectrum), to achieve higher utility in terms of revenue. Such cooperation can improve the capacity of the WRN, and thus throughput for terminal devices (TDs). However, this cooperation can be realized only if fair allocation of aggregated utility, which is the sum of the utility of all the cooperative SPs, can be achieved. In this paper, we investigate the WRN consisting of SPs at the upper layer and TDs at the lower layer and present a game theoretic framework to address the cooperation decision making problem in the WRN. Specifically, the cooperation of SPs is modeled as an overlapping coalition formation game, in which SPs should form a stable coalitional structure and obtain a fair share of the aggregated utility. We also study the problem of allocating aggregated utility based on the concept of Shapley value, which stabilizes the cooperation of SPs in the WRN. The cooperation of TDs is modeled as a network formation game, in which TDs establish links among each other to form a stable network structure. Numerical results demonstrate that the proposed distributed algorithm obtains the aggregated utility approximating the optimal solutions and achieves good convergence speed.Comment: Accepted for publication in IEEE Transactions on Vehicular Technolog