Entanglement Produced by Using Some Biparticle Bose Systems
  In this paper, the generating of entanglement by using some biparticle Bose systems acting on vacuum state are investigated. These systems include two-mode squeezed system, thermal system of a free single particle (where the fictitious tilde system is regarded another particle), and the system of two coupling harmonic oscillators. The technique of integration within an ordered product (IWOP) of operators is used. 
Xian-Ting Liang