A continuous-variable tripartite entangled state is experimentally generated by combining three independent squeezed vacuum states and the variances of its relative positions and total momentum are measured. We show that the measured values violate the separability criteria based on the sum of these quantities and prove the full inseparability of the generated state.PACS numbers: 03.65. Ud, 03.67.Mn, 42.50.Dv The remarkable proposal of quantum teleportation [1] demonstrates that the quantum correlations of a shared entangled state enable two parties to reliably exchange quantum information. So far, several experiments on quantum communication with discrete-variable states have been carried out. In the domain of continuous variables (CVs), the unconditional quantum teleportation of arbitrary coherent states [2,3,4] and quantum dense coding [5] have been demonstrated. These successful experiments show the advantage of CV bipartite entanglement for the implementation of quantum protocols; that is, the simplicity of its generation and manipulation and the applicability of efficient homodyne techniques to its detection.CV entanglement may also be applicable to quantum protocols involving more than two parties. For example, tripartite entanglement (the entanglement shared by three parties) enables one to construct a quantum teleportation network [6], to build an optimal one to two telecloner [7], or to perform controlled dense coding [8]. CV tripartite entanglement can be generated in a similar way as in the case of CV bipartite entanglement. It only requires combining three modes using linear optics, where at least one of these modes is in a squeezed state [6]. In fact, as pointed out in Ref. [9], CV tripartite entanglement has already been generated in the CV quantum teleportation experiment of Ref.[2], although no further investigation was made there. On the other hand, the separability properties of tripartite states are more complicated than in the bipartite case; three-mode Gaussian states are classified into five different classes [9]. In order to exploit the tripartite entanglement for three-party quantum protocols such as that from Ref.[6], the state involved has to be fully inseparable (class 1 in Ref. [9]). Although the output state that emerges from the beam splitters with one or more squeezed input states * Electronic address: takao@ap.t.u-tokyo.ac.jp is in principle fully inseparable for any nonzero squeezing [6], inevitable losses in the real experiment may destroy the genuine tripartite entanglement and convert the state into a partially or fully separable one. This would make a true tripartite quantum protocol fail. In other words, the success of a true tripartite quantum protocol (e.g., a coherent-state quantum teleportation network with fidelities better than one half) is a sufficient criterion for the full inseparability of the state involved [6]. It should be noted here that the success of a tripartite quantum protocol between two parties with the help of the third party (e.g., via a momentum d...

Quantum teleportation of a squeezed state is demonstrated experimentally. Due to some inevitable losses in experiments, a squeezed vacuum necessarily becomes a mixed state which is no longer a minimum uncertainty state. We establish an operational method of evaluation for quantum teleportation of such a state using fidelity, and discuss the classical limit for the state. The measured fidelity for the input state is 0.85± 0.05 which is higher than the classical case of 0.73±0.04. We also verify that the teleportation process operates properly for the nonclassical state input and its squeezed variance is certainly transferred through the process. We observe the smaller variance of the teleported squeezed state than that for the vacuum state input.

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Selective monodesilylation of 1,8-bis(t-butyldiphenylsilyl)-1,3,5,7-octatetrayne and 1,6-bis(t-butyldiphenylsilyl)-1,3,5-hexatriyne with lithiated phenylacetylene gave unstable 1-(t-butyldiphenylsilyl)-1,3,5,7-octatetrayne and 1-(t-butyldiphenylsilyl)-1,3,5-hexatriyne, respectively. The terminal acetylenes on lithiation added to aldehydes and a ketone giving polyynols in high yields. The reaction was applied to the synthesis of polyyne antibiotics, caryoynencins. Polymerization of the terminal octatetrayne on an ITO-coated glass plate gave a film, which showed conductivity of 10−4 S cm−1 when doped with SO3.

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