Gühne Otfried
Institut für Theoretische Physik, Universität Hannover, Appelstrasse 2, D-30167 Hannover, Germany.
Phys Rev Lett. 2004 Mar 19;92(11):117903. doi: 10.1103/PhysRevLett.92.117903. Epub 2004 Mar 18.
We derive a family of necessary separability criteria for finite-dimensional systems based on inequalities for variances of observables. We show that every pure bipartite entangled state violates some of these inequalities. Furthermore, a family of bound entangled states and true multipartite entangled states can be detected. The inequalities also allow us to distinguish between different classes of true tripartite entanglement for qubits. We formulate an equivalent criterion in terms of covariance matrices. This allows us to apply criteria known from the regime of continuous variables to finite-dimensional systems.
我们基于可观测量方差的不等式，推导出了有限维系统的一族必要可分性判据。我们证明，每一个纯二分纠缠态都会违背其中一些不等式。此外，还能检测出一族束缚纠缠态和真正的多方纠缠态。这些不等式还使我们能够区分量子比特不同类别的真正三方纠缠。我们根据协方差矩阵制定了一个等效判据。这使我们能够将连续变量领域已知的判据应用于有限维系统。
