Optimal control theory applied to rotational control in dissipative media and torsional control with polarization shaped pulses.

摘要

Quantum optimal control calculations were performed that determined the optimal laser pulse shapes for control over quantum mechanical rotation dynamics. This formalism was applied to control over the timing and magnitude of molecular alignment as well as the width of the alignment peak at the target time. The optimizations were then extended to the density matrix formalism where the effects of temperature and a dissipative bath were examined at the multi-level Bloch level of theory. Limits to the timescales of control in both the isolated molecule case and the dissipative case were found. Control for arbitrary rotational state superpositions was then calculated in thermal and dissipative environments and decay timescales for these states were compared to ideal cases. Further quantum optimal control calculations were done to induce uni-directional rotation of one ring relative to the other in a surface affixed bicyclic molecule with the aim of making a molecular motor driven by coherent light. This was done for the cases of linear polarization only and with a polarization shaping method that allowed for an arbitrarily polarized optimal field. It was found that optimal pulses can induce unidirectional rotation with a great deal of angular momentum by switching the direction of polarizations during the pulse from elliptically polarized in one a single direction to another multiple times.