(4)EPP based on cross-Kerr nonlinearity a. The principle of cross-Kerr nonlinearity hAnD九 ck (a|0)+b|1)a) a|0)a)+b|1)|ae") b The principle of PDc entanglement source PDC/L1H DiH+dr1v)]+rei(atb+ +a2y by )+hc (a1tHbTH +air biy tabut u2v IHIH 功hbn+a1b) Yu-Bo Sheng, Fu-Guo Deng, Hong-Yu Zhou, Phys. Rev. A77, 042308(2008)(4) EPP based on cross-Kerr nonlinearity a. The principle of cross-Kerr nonlinearity ( 0 1 ) 0 1 QND t iH ck i U e a b a b e       = + = + 1 1 1 1 2 2 2 2 [( )] ( ) . i H a b a b re a b a b H c PDC H H V V H H V V   + + + + + + + + = + + + + 1 1 1 1 2 2 2 2 ( ) 0 a b a b a b a b H H V V H H V V + + + + + + + + + + + 2 1 1 1 1 2 2 2 2 ( ) 0 a b a b a b a b H H V V H H V V + + + + + + + + + + + b. The principle of PDC entanglement source Yu-Bo Sheng, Fu-Guo Deng, Hong-Yu Zhou, Phys. Rev. A 77, 042308 (2008)