Quantum langevin equation method in non-Markovian dynamics

在2019财年，我主要研究了在相干伊辛机中产生具有强量子性质的态的可能性。这种装置可以用量子退火法模拟多体系统。然而，这种器件的输出态通常是经典的，在演化过程中不存在纠缠。这一限制使其无法应用于一般的量子信息问题。为了解决这一缺点，我们研究了在这些机器中产生具有强量子性质的态的方法。我们基于三个原因选择纠缠猫态作为目标态。首先，这种态具有很强的量子特性，因为它既有纠缠又有相干叠加。其次，伊辛机的稳态可以是细腔极限下的猫态，这样可以更方便地在这些态的基础上产生纠缠。第三，由于纠缠猫态的宏观性质，使得相干和纠缠的检测变得容易。我们目前的研究已经明确了猫态的产生，现在集中在向纠缠猫态的转换上。在产生纠缠猫态之前，高质量的猫态是必要的。因此，我们研究了耗散存在时猫态产生的条件。基于猫态的最佳参数范围，我们的研究试图找到一种实现纠缠猫态的有效方法。

In FY2019, I mainly studied the possibility of generating states with strong quantum properties in coherent Ising machine.Such devices can simulate many-body systems with quantum annealing method. However, the output states of such devices are usually classical, and there is no entanglement in the states during evolution. This limitation prevents the application to general quantum information problems. To solve this disadvantage, we study the way to generate states with strong quantum properties in these machines.We chose the entangled cat state as the target state based on three reasons. First, this state has strong quantum properties because there are both entanglement and coherent superposition in it. Second, the steady state of Ising machine can be a cat states in fine cavity limit, so that it will be more convenient to generate entanglement base on these states. Third, the detection of coherence and entanglement in an entangled cat state is easy due to its macroscopic property.Our current research has made the cat state generation clear, and now is focused on the conversion to the entangled cat state. Before generating entangled cat states, high quality cat states are necessary. Therefore, we studied the condition for cat state generating when dissipation exists. Based on the optimal parameter regimes for cat states, our research is trying to find an efficient way to achieving entangled cat states.