Efficient Construction of Photonic Quantum Computational Clusters
  We demonstrate a method of creating photonic two-dimensional cluster states that is considerably more efficient than previously proposed approaches. Our method uses only local unitaries and type-I fusion operations. The increased efficiency of our method compared to previously proposed constructions is obtained by identifying and exploiting local equivalence properties inherent in cluster states. 
Gerald Gilbert, Michael Hamrick and Yaakov S. Weinstein