弗兰克-康登阻塞对抑制囚禁离子自发辐射的理论研究

Research on the suppression of spontaneous emission in quantum systems has been a hot topic in the field of quantum optics and quantum information recently. The purpose of this project is to study the suppression the spontaneous emission in the ion-trap system by using Franck-Condon principle. The main contents are as follows: Based on the Franck-Condon blockade, the intensity of the transition between the ionic excited and ground states could be reduced by means of the strong electron-vibron coupling, which would increase the lifetime of the excited states, decrease their linewidth and suppress their spontaneous emission. Besides, experimental schemes will be designed and the impact on the fidelity of the ionic excited state would be analyzed based on realistic magnetic field gradient and other parameters in the devices. The project focuses on the combination of the theory and the experiment, which not only decreases the rate of the spontaneous emission and increases the fidelity of the preparation of the quantum state, but also helps to deepen our understanding of Franck-Condon principle and provide a theoretical reference to the physical study of multi-ion system.

抑制量子系统中自发辐射的研究是目前量子光学和量子信息的热门课题。本项目旨在利用弗兰克-康登原理（Franck-Condon principle）来抑制囚禁离子系统中的自发辐射。主要研究内容为基于弗兰克-康登阻塞效应，利用自旋相关势引起的离子内外态的强耦合来压制离子激发态和基态之间的跃迁强度，以提高激发态的寿命和降低能级线宽，从而抑制离子激发态的自发辐射。另外，本项目将结合实验装置中梯度磁场等参数的数值，研究环境对离子激发态保真度的影响，并设计实验方案。这些研究着眼于理论并结合实验进行，不仅能够降低离子激发态的自发辐射率和提高量子态制备的保真度，而且有助于深化我们对弗兰克-康登原理本身的认识，也为研究囚禁离子体系的弗兰克-康登物理提供理论参考。

针对囚禁离子的超洁净环境和高可控性，本项目以40Ca+作为研究对象，在梯度磁场的作用下产生离子激发态和基态之间的弗兰克-康登阻塞，从而在理论上探索了利用弗兰克-康登原理来抑制囚禁离子系统中的自发辐射。结合模型分型和数值模拟方法，调节磁场梯度得到系统自旋相关势引起离子内外态的强耦合，具体计算了离子激发态和基态之间弗兰克-康登因子，模拟了其随磁场梯度的变化及分析了激发态和基态之间跃迁的抑制情况，从而提高了离子激发态的寿命，在一定程度上压制了离子激发态的自发辐射。另外，采用全局操作，在非线性相互作用模型下实现海森堡极限的Mach-Zehnder干涉仪，在离子阱体系精密测量方面具有潜在的应用价值。