Coherent destruction of tunneling with optimally designed polychromatic external field

- We design polychromatic fields causing CDT.
- The field intensity is kept very low (∼105 a.u).
- We have used Floquet analysis for determining the two lowest quasi-energy states.
- SA method is used as a stochastic optimizer to minimize the energy gap.
- Quantum phase space dynamics has been obtained by using TDFGH method.

A suitably designed polychromatic field with a very low field strength and low frequency (∼10-5 atomic unit) can bring about coherent destruction of tunneling (CDT) in a symmetric double well system. It is analyzed that in the presence of an external perturbation the difference of energy between the two lowest quasi-energy states may increase or decrease depending on the spatial and temporal nature of the perturbation. We have designed sets of polychromatic fields both spatially symmetric and antisymmetric, which cause CDT in symmetric double well system. A stochastic optimizer (Simulated Annealing) has been used to design such a polychromatic field periodic in time. Both spatial symmetry preserving or symmetry breaking perturbations may cause CDT for a symmetric double well potential.