A maximum entropy principle density matrix method, valid for systems w
ith temperature different from zero, is presented making it possible t
o find two-mode squeezed states in two-level systems with relevant ope
rators and Hamiltonian connected with O(3,2). A method which allows on
e to relate the appearance of squeezing to the relevant operators, inc
luded in order to define the density matrix of the system, is given.