Experimental Entanglement of a Six-Photon Symmetric Dicke State

We report on the experimental observation and characterization of a six-photon entangled Dicke state. We obtain a fidelity as high as 0.654 +/- 0.024 and prove genuine six-photon entanglement by, amongst others, a two-setting witness yielding -0.422 +/- 0.148. This state has remarkable properties; e.g., it allows obtaining inequivalent entangled states of a lower qubit number via projective measurements, and it possesses a high entanglement persistency against qubit loss. We characterize the properties of the six-photon Dicke state experimentally by detecting and analyzing the entanglement of a variety of multipartite entangled states.