Department of Optics, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic.
Sci Rep. 2017 Mar 27;7:45045. doi: 10.1038/srep45045.
Localizability of entanglement in fully inseparable states is a key ingredient of assisted quantum information protocols as well as measurement-based models of quantum computing. We investigate the existence of fully inseparable states with nonlocalizable entanglement, that is, with entanglement which cannot be localized between any pair of subsystems by any measurement on the remaining part of the system. It is shown, that the nonlocalizable entanglement occurs already in suitable mixtures of a three-qubit GHZ state and white noise. Further, we generalize this set of states to a two-parametric family of fully inseparable three-qubit states with nonlocalizable entanglement. Finally, we demonstrate experimentally the existence of nonlocalizable entanglement by preparing and characterizing one state from the family using correlated single photons and linear optical circuit.
完全不可分离态中的纠缠局域性是辅助量子信息协议以及基于测量的量子计算模型的关键组成部分。我们研究了具有非局域纠缠的完全不可分离态的存在性，也就是说，通过对系统其余部分的任何测量，无法在任何对子系统之间局域化纠缠。结果表明，非局域纠缠已经出现在适当的三量子位 GHZ 态和白噪声混合物中。此外，我们将这组态推广到具有非局域纠缠的完全不可分离的双参数三量子比特态族。最后，我们通过使用相关单光子和线性光学电路来制备和表征该族中的一个态，从而实验证明了非局域纠缠的存在。
