Quantum dynamics and delocalization in coherently driven one-dimensional double-well system

We numerically study the influence of a polychromatic perturbation on wave packet dynamics in one-dimensional double-well potential. It is found that the time-dependence of the transition probability between the wells shows two kinds of motion typically, a coherent oscillation and an irregular fluctuation combined to the delocalization of the wave packet, depending on the perturbation parameters. The coherent motion changes the irregular one as the strength and/or the number of frequency components of the perturbation increases. We discuss a relation between our model and decoherence in comparing with the result under stochastic perturbation. Furthermore we compare the quantum fluctuation, tunneling in the quantum dynamics with the ones in the semiquantal dynamics.