52,125 research outputs found

### Structure of correlated initial states that guarantee completely positive reduced dynamics

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 $D^0\to K\pi$ decay and $y_\mathrm{CP}$ at BESIII

In this paper, I report the preliminary results of the strong phase
difference $\cos\delta_{K\pi}$ between the doubly Cabibbo-suppressed process
$\overline{D}{}^0\to K^- \pi^+$ and Cabibbo-favored $D^0\to K^- \pi^+$ at
BESIII. In addition, the preliminary results of the $D^0$-$\overline{D}{}^0$
mixing parameter $y_\mathrm{CP}$ by analyzing $CP$-tagged semileptonic $D$
decays are presented. These measurements were carried out based on the
quantum-correlated technique in studying the process of $D^0\overline{D}{}^0$
pair productions of 2.92 fb$^{-1}$ $e^+e^-$ collision data collected with the
BESIII detector at $\sqrt{s}$ = 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

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 $CP/P$
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

A graph is $n$-existentially closed ($n$-e.c.) if for any disjoint subsets
$A$, $B$ of vertices with $|{A \cup B}|=n$, there is a vertex $z \notin A \cup
B$ adjacent to every vertex of $A$ and no vertex of $B$. For a block design
with block set $\cal B$, its block intersection graph is the graph whose vertex
set is $\cal B$ 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
$2$-e.c. In particular, we study the $\lambda$-fold triple systems with
$\lambda \ge 2$ and determine for which parameters their block intersection
graphs are $1$- or $2$-e.c. Moreover, for Steiner quadruple systems, the block
intersection graphs and their analogue called $\{1\}$-block intersection graphs
are investigated, and the necessary and sufficient conditions for such graphs
to be $2$-e.c. are established.Comment: 11 page

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

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 $SO(2n)/U(n)$ and $Sp(n)/U(n)$ (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

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

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

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

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

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

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

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