title: Experimental generation of an eight-photon             Greenberger-Horne-Zeilinger state.
abstract: Multi-partite entangled states are important for developing studies of quantum                 networking and quantum computation. To date, the largest number of particles that                 have been successfully manipulated is 14 trapped ions. Yet in quantum information                 science, photons have particular advantages over other systems. In particular, they                 are more easily transportable qubits and are more robust against decoherence. Thus                 far, the largest number of photons to have been successfully manipulated in an                 experiment is six. Here we demonstrate, for the first time, an eight-photon                 Greenberger-Horne-Zeilinger state with a measured fidelity of                 0.59±0.02, which proved the presence of genuine eight-partite entanglement.                 This is achieved by improving the photon detection efficiency to 25% with a 300-mW                 pump laser. With this state, we also demonstrate an eight-party quantum                 communication complexity scenario. This eight-photon entangled-state source may be                 useful in one-way quantum computation, quantum networks and other quantum                 information processing tasks.
authors: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, China.
authors: Yun-Feng
authors: YF
authors: Huang
authors: Bi-Heng
authors: BH
authors: Liu
authors: Liang
authors: L
authors: Peng
authors: Yu-Hu
authors: YH
authors: Li
authors: Li
authors: L
authors: Li
authors: Chuan-Feng
authors: CF
authors: Li
authors: Guang-Can
authors: GC
authors: Guo