SUPPRESSION OF QUANTUM COHERENCE - NOISE EFFECT

The influence of noise on the tunneling dynamics in a periodically dri ven two-level system is discussed. To describe the noisy quantum dynam ics the stochastic Schrodinger equation is used. It accounts for the m utual influence of both phase damping and circularly polarized field d riving with a noisy amplitude. It is shown that in absence of determin istic driving, a random dynamic drive stabilizes the localized state w hile a random, non-demolition drive (see below) destabilizes the local ized state. In contrast, localization which can be induced by determin istic driving fields is destroyed by either phase damping or fluctuati ons of the driving fields. The delocalization rate for intermediate-to -strong field strength turns out to be universal. Approximate results can be obtained by a perturbation treatment. (C) 1998 Elsevier Science B.V. All rights reserved.