Gühne Otfried, Lütkenhaus Norbert
Institut für Quantenoptik und Quanteninformation, Osterreichische Akademie der Wissenschaften, Innsbruck, Austria.
Phys Rev Lett. 2006 May 5;96(17):170502. doi: 10.1103/PhysRevLett.96.170502. Epub 2006 May 1.
Entanglement detection typically relies on linear inequalities for mean values of certain observables (entanglement witnesses), where violation indicates entanglement. We provide a general method to improve any of these inequalities for bipartite systems via nonlinear expressions. The nonlinearities are of different orders and can be directly measured in experiments, often without any extra effort.
纠缠检测通常依赖于某些可观测量（纠缠见证者）平均值的线性不等式，其中违背该不等式表明存在纠缠。我们提供了一种通用方法，通过非线性表达式来改进二分系统中这些不等式中的任何一个。这些非线性具有不同的阶数，并且通常无需任何额外努力就能在实验中直接测量。
