Linear optical scheme for producing polarization-entangled NOON states
  We propose a linear optical scheme that can conditionally generate high NOON states using polarization modes. This scheme provides advantages over the previous proposals on path-entangled NOON states in view of success probability or required resources of optical elements. We also investigate two experimental schemes feasible within existing technology that can produce the NOON-like or the NOON state for N = 4. 
Su-Yong Lee, Tomasz Paterek, Hee Su Park, and Hyunchul Nha
quant-ph