We show how to prepare four-photon polarization entangled states based on
some Einstein-Podolsky-Rosen (EPR) entanglers. An EPR entangler consists of two
single photons, linear optics elements, quantum non-demolition measurement
using a weak cross-Kerr nonlinearity, and classical feed forward. This
entangler which acts as the most primary part in the construction of our scheme
allows us to make two separable polarization qubits entangled near
deterministically. Therefore, the efficiency of the present device completely
depends on that of EPR entanglers, and it has a high success probability.Comment: 5 pages, 3 figure
