连续变量系统中准对称多模高斯态的纠缠

Entanglement of quasi-symmetry multi-mode Gaussian states in continuous variable system

基于现今连续变量系统中高斯态纠缠的一些研究成果,利用负性对数为纠缠度量来讨论一个准对称的N模高斯态的纠缠问题.以一个准对称八模高斯态为例,寻找八模高斯态和与其对应的两模高斯态共变矩阵参数之间的解析关系.研究发现在多模高斯态对应两模高斯态的方案中由于省略了多模高斯态辛本征值的部分信息,导致这种方案虽然可以使多模高斯态对应为一个两模高斯态,但是这种对应关系不是唯一的,一个两模高斯态可以对应很多不同的多模高斯态,而且这些高斯态拥有着相同的纠缠信息.通过寻找八模高斯态与两模高斯态参数间的解析关系,研究发现只要确定辛本征值就能得到八模高斯态和两模高斯态参数之间的解析关系,按照这个思路可以得到N模高斯态与两模高斯态参数间的解析关系.

The entanglement of multi-mode Gaussian state in continuous variable system is investigated. In recent studies, the determination in entanglement of a general two-mode Gaussian state depend on purity measurement, and some studies have already extended it to the case of quasi-symmetry multi-mode Gaussian state. In this paper, entanglement is quantified by logarithmic negativity. The study focuses on the entanglement of quasi-symmetric eight-mode Gaussian state. Our aim is to find the analytic description of the correlation between the quasi-symmetric Gaussian state and two-mode Gaussian state. The results show that： the correlation is not unique. A two-mode Gaussian state may correspond to many different multi-mode Gaussian states, and these multi-mode Ganssian states have the same entanglement information.