MODIFICATION OF TUNNELING DYNAMICS BY THE APPLICATION OF RANDOM EXTERNAL FIELDS

We investigate the possibility of modifying the tunneling of a particl e between two states by the application of an external field. The fiel d couples to the dipole moment of the tunnel object. A phenomenologica l Hamiltonian is introduced which permits investigation of external fi elds which have both a random and a time varying systematic component. A numerical solution of the stochastic equations of motion characteri zing the population evolution is carried out by averaging over stochas tic trajectories, for a wide range of parameter values which describe the tunnel splitting and the systematic and random properties of the e xternal field. For certain limiting cases, we obtain analytic approxim ations describing the system dynamics, and compare these solutions wit h those obtained by the numerical method. We also investigate external fields that satisfy a precise connection between frequency and amplit ude, whereby the resulting Floquet quasi-energies are degenerate, and produce state populations that vary periodically in time. The fluctuat ion induced modification of the population evolution is assessed for t hese Floquet fields. We find that it is possible to control tunneling by the use of external fields, even if they have a random component.