Generation of Large Photon-Number Cat States using Linear Optics and   Quantum Memory
  A recursive method for producing path-entangled states of light is presented. These states may find applications in quantum lithography and high-precision interferometric measurements. The required resources are single-photon sources, linear optics components, and photodetectors. Adding a quantum memory greatly enhances the yield in comparison with the previously known schemes. 
N. J. Cerf, J. Fiurasek, S. Iblisdir, and S. Massar