Greenberger-Horne-Zeilinger-type violation of local realism by mixed states

Date: 2008-12-30
Authors Xiao-Qi Zhou, Chao-Yang Lu, Wei-Bo Gao, Jin Zhang, Zeng-Bing Chen, Tao Yang, and Jian-Wei Pan
Journal No. Phys. Rev. A 78, 012112 (2008)  
Abstract Cluster states are multiparticle entangled states with special entanglement properties particularly suitable for quantum computation. It has been shown that cluster states can exhibit Greenberger-Horne-Zeilinger (GHZ) -type nonlocality even when some of their qubits have been lost. In the present work, we generated a four-photon mixed state, which is equivalent to the partial, qubit-loss state of an N-qubit cluster state up to some local transformations. By using this mixed state, we then realize a GHZ-type violation of local realism. Our results not only demonstrate a mixed state’s GHZ-type nonlocality but also exhibit the robustness of cluster states under qubit-loss conditions.