近日，波兰华沙大学的Danish Ali Hamza与Jan Chwedeńczuk合作并取得一项新进展。经过不懈努力，他们揭示量子临界点附近热完全连接自旋链的贝尔关联性。相关研究成果已于2024年7月11日在国际知名学术期刊《物理评论A》上发表。

本文详细分析了具有粒子交换对称性的多量子比特系统中多体贝尔关联的特征和强度。这样的构型可以用一个有效的类薛定谔方程来描述，它允许精确的解析预测。研究表明，在量子临界点附近，这些关联很快变得如此强烈，以至于只有一小部分量子比特保持不关联。研究人员还确定了热波动破坏贝尔关联的阈值温度。他们希望这里提出的方法，由于它的普遍性，将对即将到来的真正非经典贝尔关联复杂系统的研究有用。

据悉，贝尔关联是量子力学表现自身的最奇特的现象之一。它们的存在表明，该系统可能违反了局部实在论的假设——这种假设曾被认为是物质世界不可争辩的属性。从这个基本观点来看，贝尔关联的重要性在其应用中得到了进一步的阐明，从量子密码学到量子计量学和量子计算。因此，对复杂的、可扩展的多体系统的“贝尔内容”进行表征是人们越来越感兴趣的。

附：英文原文

Title: Bell correlations of a thermal fully connected spin chain in the vicinity of a quantum critical point

Author: Danish Ali Hamza, Jan Chwedeńczuk

Issue&Volume: 2024/07/11

Abstract: Bell correlations are among the most exotic of the phenomena through which quantum mechanics manifests itself. Their presence signals that the system may violate the postulates of local realism—conjectures once thought to be to be a non-negotiable property of the physical world. The importance of Bell correlations from this fundamental point of view is even further clarified by their applications, ranging from quantum cryptography to quantum metrology and quantum computing. It is therefore of growing interest to characterize the “Bell content” of complex, scalable many-body systems. Here, we perform a detailed analysis of the character and strength of many-body Bell correlations in interacting multiqubit systems with particle exchange symmetry. Such a configuration can be described by an effective Schrdinger-like equation, which allows precise analytical predictions. We show that in the vicinity of the quantum critical point, these correlations quickly become so strong that only a fraction of the qubits remain uncorrelated. We also identify the threshold temperature above which thermal fluctuations destroy Bell correlations. We hope that the approach presented here, due to its universality, will be useful for upcoming research on genuinely nonclassical Bell-correlated complex systems.

DOI: 10.1103/PhysRevA.110.012210

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.012210