N量子比特系统的纠缠判据

Entanglement criterion of N qubit system

在前文(2019 Int. J.Mod.Phys.B 33 1950197;2020 Int.J.Mod.Phys.B 34 2050022)中,我们提出了一种判断2量子比特系统纠缠的方法,2量子比特系统可分的充分必要条件是相关系数为正且主密度矩阵可分,否则系统纠缠.在本文中,通过数值计算与讨论,先将2量子比特系统纠缠判据的方法推广到3量子比特系统中去;接着,继续将3量子比特系统推广到N量子比特系统中去.这是一个复杂而有趣的问题.

In previous paper(2019 Int.J.Mod.Phys.B 33 1950197;2020 Int.J.Mod.Phys.B 34 2050022),we presented a method to judge the entanglement of 2-qubit system.The necessary and sufficient conditions for the 2qubit system being separable are that if the relevant coefficients is positive and the principal density matrix is separable,then the system is separable,otherwise it is entangled.Now in this paper,we try to generalize this criterion to a 3-qubit system,and then,we further generalize the criterion of 3-qubit system to an N-qubit system.This is a complicated and interesting issue.