# Experimental analysis of a four-qubit photon cluster state.

@article{Kiesel2005ExperimentalAO, title={Experimental analysis of a four-qubit photon cluster state.}, author={Nikolai Kiesel and Christian Schmid and Ulrich Weber and G{\'e}za T{\'o}th and Otfried G{\"u}hne and Rupert Ursin and Harald Weinfurter}, journal={Physical review letters}, year={2005}, volume={95 21}, pages={ 210502 } }

Linear-optics quantum logic operations enabled the observation of a four-photon cluster state. We prove genuine four-partite entanglement and study its persistency, demonstrating remarkable differences from the usual Greenberger-Horne-Zeilinger (GHZ) state. Efficient analysis tools are introduced in the experiment, which will be of great importance in further studies on multiparticle entangled states.

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