MODIFICATION OF TUNNELING DYNAMICS BY THE APPLICATION OF RANDOM EXTERNAL FIELDS

We investigate the possibility of modifying the tunneling of a particle between two states by the application of an external field. The field couples to the dipole moment of the tunnel object. A phenomenological Hamiltonian is introduced which permits investigation of external fields which have both a random and a time varying systematic component. A numerical solution of the stochastic equations of motion characterizing the population evolution is carried out by averaging over stochastic trajectories, for a wide range of parameter values which describe the tunnel splitting and the systematic and random properties of the external field. For certain limiting cases, we obtain analytic approximations describing the system dynamics, and compare these solutions with those obtained by the numerical method. We also investigate external fields that satisfy a precise connection between frequency and amplitude, whereby the resulting Floquet quasi-energies are degenerate, and produce state populations that vary periodically in time. The fluctuation induced modification of the population evolution is assessed for these Floquet fields. We find that it is possible to control tunneling by the use of external fields, even if they have a random component.