Dissipative Tunneling through a Fluctuating Barrier: Quantum State Diffusion Approach

We investigate the problem of dissipative tunneling across a randomly modulated barrier in the two-level approximation and within the quantum state diffusion approach. Introducing the Bloch sphere of all possible pure states of the system we analyse numerically the behaviour of stochastic quantum trajectories. If the barrier is static the coherent tunneling is suppressed by two types of diffusion; the state dependent one along the meridians of the sphere and the uniform one along its latitudes. The barrier fluctuations forced by dichotomic noise increases the first kind of diffusion. The strongest suppression of coherency occurs when the jump rate of the noise equals the amplitude of fluctuations. For large enough amplitudes we observe the decrease of the variance of two components of the Bloch vector, after the complete decay of their mean values.