Atomic systems squeezed vacuum states

The state (79) is called a two-photon entangled state. In Section VI, we will discuss another method of preparing the system in the two-photon entangled state based on the interaction of two atoms with a squeezed vacuum field. 

In order to calculate the stationary state of the two-atom system, we have to know the steady-state populations pu of the collective atomic states and the coherencies Py(i 7 j)- First, we consider a system of two identical atoms (A = 0, Tj = r2) separated by an arbitrary distance rn and interacting with a squeezed vacuum field. Moreover, we assume that the carrier frequency (as of the squeezed vacuum field is resonant to the atomic transition frequencies (0)s = Mo). 

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