Abstract:A wide area quantum key distribution (QKD) network deployed on communication infrastructures provided by China Mobile Ltd. is demonstrated. Three cities and two metropolitan area QKD networks were linked up to form the Hefei-Chaohu-Wuhu wide area QKD network with over 150 kilometers coverage area, in which Hefei metropolitan area QKD network was a typical full-mesh core network to offer all-to-all interconnections, and Wuhu metropolitan area QKD network was a representative quantum access network with point-to-multipoint configuration. The whole wide area QKD network ran for more than 5000 hours, from 21 December 2011 to 19 July 2012, and part of the network stopped until last December. To adapt to the complex and volatile field environment, the Faraday-Michelson QKD system with several stability measures was adopted when we designed QKD devices. Through standardized design of QKD devices, resolution of symmetry problem of QKD devices, and seamless switching in dynamic QKD network, we realized the effective integration between point-to-point QKD techniques and networking schemes. 449-449 (1995). 4. R. J. Hughes, G. G. Luther, G. L. Morgan, C. G. Peterson, and C. Simmons, "Quantum cryptography over underground optical fibers," Lecture Notes in Computer Science, 1109, 329-342 (1996).5. P. D. Townsend, "Simultaneous quantum cryptographic key distribution and conventional data transmission over installed fibre using wavelength-division multiplexing," Electron. Lett. 33, 188-190 (1997

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.

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Fast and effective removal of elemental mercury in a wide temperature range is critical for the smelting industry. In this work, a recyclable magnetic iron sulfide/selenide sorbent is developed to capture and recover Hg 0 from smelting flue gas. Benefiting from Se doping, the Hg 0 capture performance of prepared FeS x Se y is significantly enhanced compared with traditional iron sulfide, especially at high temperatures. Considering the recyclability and working temperature, FeS 1.32 Se 0.11 exhibits the best Hg 0 capture performance. The average capture rate of FeS 1.32 Se 0.11 is 3.661 μg/g/min at 80 °C and its saturation adsorption capacity is 20.216 mg/g. The flue gas compositions have almost no effect on Hg 0 capture. X-ray photoelectron spectroscopy and mercury thermal programmed desorption suggest that the stable active Se−S n 2− adsorption site can combine with Hg 0 to form HgSe, consequently improving Hg 0 capture performance at high temperatures. After Hg 0 capture, the spent FeS x Se y can be collected by magnetic separation and regenerated through selective extraction, which facilitates harmless treatment and resource reuse of mercury. With the advantages of excellent Hg 0 capture performance, wide operating temperature range, and remarkable recycling property, FeS x Se y microparticles may be a promising sorbent for Hg 0 capture in industrial applications, while opening a new avenue to realize the resource utilization toward toxic elements.