Effective Hamiltonian theory and its applications in quantum information

This paper presents a useful compact formula for deriving an effective Hamiltonian describing the time-averaged dynamics of detuned quantum systems. The formalism also works for ensemble-averaged dynamics of stochastic systems. To illustrate the technique, we give examples involving Raman processes, Bloch-Siegert shifts, and quantum logic gates. PACS Nos: 03.65.–w