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Experimental observation of four-photon entanglement from down-conversion

M. Eibl·S. Gaertner·M. Bourennane·Ch. Kurtsiefer·M. Zukowski·H. Weinfurter
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Abstract

We observe polarization-entanglement between four photons produced from a single down-conversion source. The non-classical correlations between the measurement results violate a generalized Bell inequality for four qubits. The characteristic properties and its easy generation with high interferometric contrast make the observed four-photon state well-suited for implementing advanced quantum communication schemes such as multi-party quantum key distribution, secret sharing and telecloning.

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M. Eibl, S. Gaertner, M. Bourennane, Ch. Kurtsiefer, M. Zukowski, H. Weinfurter. 2003-02-05. Experimental observation of four-photon entanglement from down-conversion. https://doi.org/10.1103/physrevlett.90.200403

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