The exact WKB analysis on correlation functions of low dimensional quantum systems and quantum entanglement.

我们发展了一种新的公式，在有限温度下对一维量子系统的关联函数进行精确的定量研究。这是通过将量子转移方法和精确的WKB方法相结合来实现的，该公式使我们能够对量子关联进行严格的数值研究。作为一个具体的例子，我们将其应用到自旋1/2量子XXZ链中，观察到关联函数和量子纠缠的行为随着系统温度和外加磁场的变化而变化。

We develop a novel formulation in an exact quantitative study on the correlation functions of 1D quantum systems at finite temperature. This is accomplished by combining the quantum transfer method and the exact WKB method.The formulation enables us to carry a rigorous numerical study on the quantum correlations. As a concrete example, we apply it to the spin 1/2 quantum XXZ chain.The variety of behaviors of the correlation functions and quantum entanglement is observed as we change the system temperature and an applied magnetic field.