耗散腔QED系统在量子模拟中的应用研究

The biggest obstacle for quantum manipulation is the dissipation induced by the coupling between quantum systems and the environment, which spoils or even eliminates the useful quantum effects. This project is based on cavity QED systems, and, by employing the dissipation, one of its destructive factors, in preparing multiple atom many-body quantum states and in exploring novel quantum phases, providing a typical paradigm that the dissipation can be applied for the aspects of simulating strongly correlated systems with the controllable physical systems. The project respectively investigates the cases of multiple atoms interacting with a single dissipative cavity, a one-dimensional dissipative cavity array, and a two-dimensional dissipative cavity array, studying how to control the system's parameters, as to make the system's unitary dynamics and dissipative dynamics commonly induce a specific irreversible dynamics process, thus driving these atoms to the expected many-body quantum states and novel quantum phases. As the engineered irreversible dynamics process uses the dissipation as a positive resource, the obtained many-body quantum states and novel quantum phases are robust against decoherence. In addition, the irreversible dynamics process is only dependent on the relationship between different parameters but not on their exact values. Also, it is independent on multiple atom system's initial state. This thus greatly relaxes the requirement for the experimental condition.

实现量子操控最大的障碍是量子系统与环境耦合所导致的耗散，它会破坏甚至消除量子系统有用的量子效应。本课题基于腔QED系统，并把该系统的破坏因素之一的耗散利用于制备多原子多体量子态以及探索新奇量子相，为耗散在可控物理系统模拟强关联体系方面的应用提供了一个典型范例。本课题依次研究多个受驱动原子与单个耗散腔、与一维耗散腔链、以及与二维耗散腔链的耦合，研究如何通过控制系统的参量，使得系统的幺正动力学与耗散动力学共同诱导出特定的不可逆动力学过程，从而把多个原子驱动到所期待的多体量子态或者新奇量子相。由于所构造的不可逆动力学过程把耗散当做积极的因素加以利用，因此所得到的多体量子态以及新奇量子相对消相干不敏感；此外，它只取决于参量之间的关系而不是精确值，同时也不依赖于多原子体系的初始态。这在很大程度上放宽了对实验条件的要求。

量子系统与环境的耦合导致耗散，往往会减弱甚至消除量子系统本身的量子效应。本项目基于腔量子电动力学，计划研究多个受驱动的原子与单个耗散腔以及耦合耗散腔的耦合机制，从而实现多原子稳态以及可能的量子相变行为。在本项目的实施中，我们首先研究了相互耦合的两个开放腔系统，每个腔中囚禁一个三能级原子，并分别受外场的驱动；通过设置特定的腔场光子衰竭辅助的驱动机制，实现了两个分离原子的高保真度的稳态纠缠。其次，我们研究了两个两能级系统与单个耗散腔的耦合机制，通过外场泵浦邻近低激发数的缀饰基，并优化腔场耗散诱导的不可逆动力学，实现了把特定初始态的原子驱动到高保真度的稳态纠缠。由于使用的是更简单的两能级系统，该方案更有可能在实验上实现。我们还进一步研究了多个两两耦合的开放腔链系统，初步发现了该系统的动力学可以实现更有意义的多体稳态纠缠甚至相变行为，更深入的研究还在进行当中。