Experimental observation of an entire family of four-photon entangled   states
  A single linear optical set-up is used to observe an entire family of four-photon entangled states. This approach breaks with the inflexibility of present linear-optical set-ups usually designed for the observation of a particular multi-partite entangled state only. The family includes several prominent entangled states that are known to be highly relevant for quantum information applications. 
Witlef Wieczorek, Christian Schmid, Nikolai Kiesel, Reinhold Pohlner,   Otfried G\"uhne, Harald Weinfurter