Quantum langevin equation method in non-Markovian dynamics

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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.