General two-mode squeezed states

The states|A₁A₂ are considered, where the operators are associated with a unitary representation of the groupSp(4,), and the two-mode Glauber coherent states |A₁A₂> are joint eigenstates of the destruction operatorsa₁ anda₂ for the two independent oscillator modes. We show that they are ordinary coherent states with respect to new operatorsb₁ andb₂, which are themselves general linear (Bogolibov) transformations of the original operatorsa₁,a₂ and their hermitian conjugatesa¹,a². We further show how they may be regarded as the most general two-mode squeezed states. Most previous work on two-mode squeezed states appears to be based on more restrictive definitions than our own, and thereby reduces to special cases which are unified within our treatment.