Quantum tunneling effect occurs often in condensed matter physics, examples are JJs, heteronanostructures, etc.. The tunneling effect plays an important role in the nonlinear relaxation time from a metastable state in an open quantum system, interacting with a thermal bath. Symmetrical and asymmetric bistable systems are good quantum model systems for analysis of the "superconducting quantum bits" and decoherence phenomena. To obtain very long coherence times in the presence of interaction between the qubit and the noisy environment is one of the greatest challenges of physics. The inf1uence of the environment in quantum tunneling has been in the focus of intense research over the last years -. The environment is commonly described as an ensemble of harmonic oscillators (thermal bath) at thermal equilibrium at temperature T, with a bilinear coupling between the quantum system and the thermal bath. By this kind of coupling between system and environment the quantum mechanical analogue of the generalized Langevin equation can be derived . Time dependent driving fields, such as laser beams, have most interesting implications for quantum systems. These time-dependent fields give rise to interesting effects, such as the coherent destruction of tunneling, the effect of quantum stochastic resonance, and the control and reduction of decoherence in open quantum systems. In this work we analyze a timedependent asynmmetric bistable potential by using the approach of the Feynman-Vemon functional in discrete variable representation (DVR)[9,10]. We calculate the quantum relaxation time for different values of the asymmetry parameter of the potential profile and different temperatures.
|Stato di pubblicazione||Published - 2010|