Zhang Zuo-Yuan, Liu Jin-Ming, Hu Zhengfeng, Wang Yuzhu
Opt Express. 2019 Sep 16;27(19):26588-26599. doi: 10.1364/OE.27.026588.
Quantum entanglement and coherence are both essential physical resources in quantum theory. Cold polar molecules have long coherence time and strong dipole-dipole interaction and thus have been suggested as a platform for quantum information processing. In this paper, we employ the pendular states of the polar molecules trapped in static electric fields as the qubits, and put forward several theoretical schemes to generate the entanglement and coherence for two coupled dipoles by using optimal control theory. Through the designs of appropriate laser pulses, the transitions from the ground state to the Bell state and maximally coherent state can be realized with high fidelities 0.9906 and 0.9943 in the two-dipole system, respectively. Meanwhile, we show that the degrees of entanglement and coherence between the two pendular qubits are effectively enhanced with the help of optimized control fields. Furthermore, our schemes are generalized to the preparation of the Hardy state and even to the creation of arbitrary two-qubit states. Our findings can shed some light on the implementation of quantum information tasks with the molecular pendular states.
量子纠缠和相干性都是量子理论中至关重要的物理资源。冷极性分子具有较长的相干时间和强偶极-偶极相互作用，因此被提议作为量子信息处理的一个平台。在本文中，我们将捕获在静电场中的极性分子的摆动态用作量子比特，并利用最优控制理论提出了几种为两个耦合偶极生成纠缠和相干性的理论方案。通过设计适当的激光脉冲，在双偶极系统中分别以0.9906和0.9943的高保真度实现从基态到贝尔态以及最大相干态的跃迁。同时，我们表明在优化控制场的帮助下，两个摆动量子比特之间的纠缠度和相干度得到了有效增强。此外，我们的方案被推广到哈迪态的制备，甚至任意两量子比特态的创建。我们的研究结果可为利用分子摆动态实现量子信息任务提供一些启示。
