We propose a reliable analytical method to evaluate the non-classical correlations based on linear entropy for an arbitrary qudit–qubit quantum state. The linear entropy is used to overcome the difficulty of the maximization of the classical correlations encountered when the von Neumann entropy is used in determining quantum discord. The quantum discord based on linear entropy is employed to derive the amount of quantum correlations in a qutrit–qubit mixed spin system in the thermal equilibrium at temperature T. We investigate also the situation when the system is embedded in an external magnetic field. The obtained amount of quantum discord is then compared with the measurement-induced disturbance (MID) and logarithmic negativity. The analysis shows that both QD and MID are more robust than entanglement. Besides, QD and MID can be exploited to determine the critical points of quantum phase transitions in the system.

中文翻译：

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基于线性熵和Qutrit-Qubit混合自旋链的热负性的量子不和谐

我们提出了一种可靠的分析方法，用于评估基于线性熵的任意qudit-qubit量子态的非经典相关性。线性熵用于克服将冯·诺依曼熵用于确定量子失调时遇到的经典相关性最大化的困难。基于线性熵的量子失调被用于导出温度为T时热平衡的qutrit-qubit混合自旋系统中的量子相关量。。我们还将调查系统嵌入外部磁场中的情况。然后将获得的量子不和谐量与测量引起的干扰（MID）和对数负性进行比较。分析表明，QD和MID都比纠缠更健壮。此外，可以利用QD和MID来确定系统中量子相变的临界点。