MIXED QUANTUM-CLASSICAL VERSUS FULL QUANTUM DYNAMICS - COUPLED QUASI-PARTICLE-OSCILLATOR SYSTEM

The relation between the dynamical properties of a coupled quasipartic le-oscillator system in the mixed quantum-classical and fully quantize d descriptions is investigated. The system is considered as a model fo r applying a stepwise quantization. Features of the nonlinear dynamics in the mixed description such as the presence of a separatrix structu re or regular and chaotic motion are shown to be reflected in the evol ution of the quantum state vector of the fully quantized system. In pa rticular, it is demonstrated how wave packets propagate along the sepa ratrix structure of the mixed description, and that chaotic dynamics l eads to a strongly entangled quantum state vector. Special emphasis is given to viewing the system from a dynamical Born-Oppenheimer approxi mation defining integrable reference oscillators, and elucidating the role of the nonadiabatic couplings which complement this approximation into a rigorous quantization scheme.