3,960 research outputs found

    Distinguishability and indistinguishability by LOCC

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    We show that a set of linearly independent quantum states {(Um,nI)ρAB(Um,nI)}m,n=0d1\{(U_{m,n}\otimes I)\rho ^{AB}(U_{m,n}^{\dagger}\otimes I)\}_{m,n=0}^{d-1}, where Um,nU_{m,n} are generalized Pauli matrices, cannot be discriminated deterministically or probabilistically by local operations and classical communications (LOCC). On the other hand, any ll maximally entangled states from this set are locally distinguishable if l(l1)2dl(l-1)\le 2d. The explicit projecting measurements are obtained to locally discriminate these states. As an example, we show that four Werner states are locally indistinguishable.Comment: 5 page

    Nonconcave penalized likelihood with a diverging number of parameters

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    A class of variable selection procedures for parametric models via nonconcave penalized likelihood was proposed by Fan and Li to simultaneously estimate parameters and select important variables. They demonstrated that this class of procedures has an oracle property when the number of parameters is finite. However, in most model selection problems the number of parameters should be large and grow with the sample size. In this paper some asymptotic properties of the nonconcave penalized likelihood are established for situations in which the number of parameters tends to \infty as the sample size increases. Under regularity conditions we have established an oracle property and the asymptotic normality of the penalized likelihood estimators. Furthermore, the consistency of the sandwich formula of the covariance matrix is demonstrated. Nonconcave penalized likelihood ratio statistics are discussed, and their asymptotic distributions under the null hypothesis are obtained by imposing some mild conditions on the penalty functions

    Erratum: Dynamics of the Bounds of Squared Concurrence [Phys. Rev. A 79, 032306 (2009)]

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    This is an erratum to our paper.Comment: a little different from the published versio