Local transformation of two EPR photon pairs into a three-photon W state
  We propose and experimentally demonstrate a transformation of two EPR photon pairs distributed among three parties into a three-photon W state using local operations and classical communication. We then characterize the final state using quantum state tomography on the three-photon state and on its marginal bipartite states. The fidelity of the final state to the ideal W state is $0.778\pm 0.043$ and the expectation value for its witness operator is $-0.111\pm 0.043$ implying the success of the proposed local transformation. 
Toshiyuki Tashima, Tetsuroh Wakatsuki, Sahin Kaya Ozdemir, Takashi   Yamamoto, Masato Koashi, Nobuyuki Imoto