State Key Laboratory of Precision, East China Normal University, Shanghai 200062, China.
Phys Chem Chem Phys. 2018 May 9;20(18):13008-13029. doi: 10.1039/c8cp00231b.
Optimal control simulations are performed for orientation and entanglement of two dipole-dipole coupled identical quantum rotors. The rotors at various fixed separations lie on a model non-interacting plane with an applied control field. It is shown that optimal control of orientation or entanglement represents two contrasting control scenarios. In particular, the maximally oriented state (MOS) of the two rotors has a zero entanglement entropy and is readily attainable at all rotor separations. Whereas, the contrasting maximally entangled state (MES) has a zero orientation expectation value and is most conveniently attainable at small separations where the dipole-dipole coupling is strong. It is demonstrated that the peak orientation expectation value attained by the MOS at large separations exhibits a long time revival pattern due to the small energy splittings arising form the extremely weak dipole-dipole coupling between the degenerate product states of the two free rotors. Moreover, it is found that the peak entanglement entropy value attained by the MES remains largely unchanged as the two rotors are transported to large separations after turning off the control field. Finally, optimal control simulations of transition dynamics between the MOS and the MES reveal the intricate interplay between orientation and entanglement.
对两个偶极-偶极耦合的相同量子转子的取向和纠缠进行了最优控制模拟。在具有施加控制场的模型非相互作用平面上，各种固定分离的转子位于。结果表明，取向或纠缠的最佳控制代表了两种对比的控制情况。特别是，两个转子的最大取向态（MOS）具有零纠缠熵，并且在所有转子分离处都很容易达到。相比之下，对比的最大纠缠态（MES）具有零取向期望值，并且在偶极-偶极耦合较强的小分离处最容易达到。结果表明，由于来自两个自由转子的简并产物态之间的极弱偶极-偶极耦合引起的小能隙，MOS 在大分离处达到的最大取向期望值表现出长时间的恢复模式。此外，发现当控制场关闭后，MES 达到的最大纠缠熵值保持基本不变，因为两个转子被传输到较大的分离。最后，MOS 和 MES 之间的跃迁动力学的最优控制模拟揭示了取向和纠缠之间的复杂相互作用。
