Maximal entanglement of squeezed vacuum states via swapping with   number-phase measurement
  We propose a method to refine entanglement via swapping from a pair of squeezed vacuum states by performing the Bell measurement of number sum and phase difference. The resultant states are maximally entangled by adjusting the two squeezing parameters to the same value. We then describe the teleportation of number states by using the entangled states prepared in this way. 
Akira Kitagawa, Katsuji Yamamoto