Classical equations for quantum squeezing and coherent pumping by the time-dependent quadratic Hamiltonian
A. F. R. de Toledo Piza · Physical Review A · 1995
The time evolution, under the general time-dependent quadratic quantum Hamiltonian, of mean values of a class of observables that includes the field quadratures and their dispersions, is obtained exactly in classical Hamiltonian form. Quantum states are described in terms of density operators, so that arbitrary initial states (both pure states and statistical mixtures) are allowed.