Quantum langevin equation method in non-Markovian dynamics

FY2019主要研究在相干伊辛机中产生强量子特性态的可能性。该装置可以用量子退火方法模拟多体系统。然而，这些器件的输出状态通常是经典的，并且在演化过程中状态中不存在纠缠。这一限制阻碍了对一般量子信息问题的应用。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特性的状态的方法。我们选择纠缠猫状态作为目标状态有三个原因。首先，这种状态具有很强的量子特性，因为其中既有纠缠态又有相干叠加态。其次，伊辛机的稳态可以是精细腔限制下的cat态，这样更便于基于这些态产生纠缠。第三，由于纠缠态的宏观特性，很容易检测到纠缠态的相干性和纠缠性。我们目前的研究已经明确了猫态的生成，现在的重点是向纠缠猫态的转换。在产生纠缠猫态之前，需要高质量的猫态。因此，我们研究了存在耗散时产生cat态的条件。我们的研究是基于最优的猫态参数制度，试图找到一种有效的方法来实现纠缠猫态。

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.