Gabay, M., & Triscone, J. - M. (2011). Superconductors: Terahertz superconducting switch. Nat. Photon., 5(8), 447–449.
Abstract: The use of terahertz pulses to 'gate' interlayer charge transport in a superconductor could lead to a variety of new and interesting applications.
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Yao, X. - C., Wang, T. - X., Xu, P., Lu, H., Pan, G. - S., Bao, X. - H., et al. (2012). Observation of eight-photon entanglement. Nat. Photon., 6(4), 225–228.
Abstract: The creation of increasingly large multipartite entangled states is not only a fundamental scientific endeavour in itself, but is also the enabling technology for quantum information. Tremendous experimental effort has been devoted to generating multiparticle entanglement with a growing number of qubits. So far, up to six spatially separated single photons have been entangled based on parametric downconversion. Multiple degrees of freedom of a single photon have been exploited to generate forms of hyper-entangled states. Here, using new ultra-bright sources of entangled photon pairs, an eight-photon interferometer and post-selection detection, we demonstrate for the first time the creation of an eight-photon Schrödinger cat state with genuine multipartite entanglement. The ability to control eight individual photons represents a step towards optical quantum computation, and will enable new experiments on, for example, quantum simulation, topological error correction and testing entanglement dynamics under decoherence.
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Zhang, Q., Goebel, A., Wagenknecht, C., Chen, Y. - A., Zhao, B., Yang, T., et al. (2006). Experimental quantum teleportation of a two-qubit composite system. Nat. Phys., 2(10), 678–682.
Abstract: Quantum teleportation, a way to transfer the state of a quantum system from one location to another, is central to quantum communication and plays an important role in a number of quantum computation protocols. Previous experimental demonstrations have been implemented with single photonic or ionic qubits. However, teleportation of single qubits is insufficient for a large-scale realization of quantum communication and computation. Here, we present the experimental realization of quantum teleportation of a two-qubit composite system. In the experiment, we develop and exploit a six-photon interferometer to teleport an arbitrary polarization state of two photons. The observed teleportation fidelities for different initial states are all well beyond the state estimation limit of 0.40 for a two-qubit system. Not only does our six-photon interferometer provide an important step towards teleportation of a complex system, it will also enable future experimental investigations on a number of fundamental quantum communication and computation protocols
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Lu, C. - Y., Zhou, X. - Q., Gühne, O., Gao, W. - B., Zhang, J., Yuan, Z. - S., et al. (2007). Experimental entanglement of six photons in graph states. Nat. Phys., 3(2), 91–95.
Abstract: Graph states-multipartite entangled states that can be represented by mathematical graphs-are important resources for quantum computation, quantum error correction, studies of multiparticle entanglement and fundamental tests of non-locality and decoherence. Here, we demonstrate the experimental entanglement of six photons and engineering of multiqubit graph states. We have created two important examples of graph states, a six-photon Greenberger-Horne-Zeilinger state, the largest photonic Schrödinger cat so far, and a six-photon cluster state, a state-of-the-art `one-way quantum computer'. With small modifications, our method allows us, in principle, to create various further graph states, and therefore could open the way to experimental tests of, for example, quantum algorithms or loss- and fault-tolerant one-way quantum computation.
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Ursin, R., Tiefenbacher, F., Schmitt-Manderbach, T., Weier, H., Scheidl, T., Lindenthal, M., et al. (2007). Entanglement-based quantum communication over 144km. Nat. Phys., 3(7), 481–486.
Abstract: Quantum entanglement is the main resource to endow the field of quantum information processing with powers that exceed those of classical communication and computation. In view of applications such as quantum cryptography or quantum teleportation, extension of quantum-entanglement-based protocols to global distances is of considerable practical interest. Here we experimentally demonstrate entanglement-based quantum key distribution over 144km. One photon is measured locally at the Canary Island of La Palma, whereas the other is sent over an optical free-space link to Tenerife, where the Optical Ground Station of the European Space Agency acts as the receiver. This exceeds previous free-space experiments by more than an order of magnitude in distance, and is an essential step towards future satellite-based quantum communication and experimental tests on quantum physics in space.
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