Applicability of a classical local control method to a quantum system Original Research Article

Quantum control of chemical reaction dynamics in a classical way derived in a previous study [J. Chem. Phys. 113 (2000) 3510] is extended by taking into account the distribution of the classical particles. Three types of control field expression are considered. The first type is designed to control a specific particle that is initially located at the center of the distribution in phase space. The second one is designed to control an effective particle with ensemble-averaged coordinates and their conjugate momentum. The third one is obtained by averaging over the fields controlling each particle of the ensemble. These are applied to a reaction system whose potential is of a one-dimensional double well. The third type of control field significantly improves the reaction yield in the presence of a bifurcation compared with the case in which the distribution is not considered. A control field for quantum wave packet dynamics is obtained by replacing the classical ensemble-averaged position and momentum with quantum mechanically averaged ones. The reaction control is explained in terms of a quantum state-to-state transition mechanism. This is proved by analyzing the time-resolved spectrum of the control field.