Time-Dependent Photon Statistics in Variable Media
  We find explicit solutions of the Heisenberg equations of motion for a quadratic Hamiltonian, describing a generic model of variable media, in the case of multi-parameter squeezed input photon configuration. The corresponding probability amplitudes and photon statistics are also derived in the Schroedinger picture in an abstract operator setting of the quantum electrodynamics (QED). Their time evolution is given in terms of solutions of certain Ermakov-type system. The unitary transformation and an extension of the squeeze/evolution operator are introduced formally. 
Sergey I. Kryuchkov, Erwin Suazo, and Sergei K. Suslov
quant-ph