Mixed Quantum-Classical versus Full Quantum Dynamics: Coupled Quasiparticle-Oscillator System

The relation between the dynamical properties of a coupled quasiparticle-oscillator system in the mixed quantum-classical and fully quantized descriptions is investigated. The system is considered to serve as a model system for applying a stepwise quantization. Features of the nonlinear dynamics of the mixed description such as the presence of a separatrix structure or regular and chaotic motion are shown to be reflected in the evolution of the quantum state vector of the fully quantized system. In particular it is demonstrated how wave packets propagate along the separatrix structure of the mixed description and that chaotic dynamics leads to a strongly entangled quantum state vector. Special emphasis is given to view the system from a dynamical Born-Oppenheimer approximation defining integrable reference oscillators and elucidating the role of the nonadiabatic couplings which complements this approximation into a rigorous quantization scheme.