Physical Review A
Quantum time-dependent perturbation theory for the construction of operator invariants
Harry R. Lewis, W. E. Lawrence
Abstract
A time-dependent perturbation theory is presented for constructing operator invariants iteratively when a Hamiltonian consists of a time-independent zeroth-order term plus a time-dependent perturbation. The procedure uses a single canonical transformation that involves an invariant operator that is canonically conjugate to the zeroth-order Hamiltonian. Such an invariant operator has recently been constructed for the case in which the zeroth-order Hamiltonian describes a harmonic oscillator.