标题： 通过两体贝尔关联器探究非平衡物理 显示英文标题

标题： Probing non-equilibrium physics through the two-body Bell correlator

摘要： 从系统动力学中识别平衡临界性和相位，被称为动力学量子相变（DQPT），当仅依赖局部可观测量时是一个具有挑战性的任务。 我们展示出，实验上可访问的两体贝尔算符，最初设计用于检测量子态中的非局域关联，在受到磁场作用的长程（LR）XY自旋链中，作为DQPT的有效见证者，其中相互作用强度按幂律衰减。 在系统参数突然淬火后，邻近自旋之间的贝尔算符在临界边界处表现出显著的下降。 在本研究中，我们考虑两种淬火协议，即磁场强度和相互作用衰减率的突然淬火。 这种明显的行为定义了一个阈值，区分了相内淬火和相间淬火，在长程相互作用强度、各向异性和系统大小变化时仍然有效。 比较分析进一步表明，传统的经典和量子关联量，包括纠缠，在动力学过程中无法捕捉到这一转变。 显示英文摘要

摘要： Identifying equilibrium criticalities and phases from the dynamics of a system, known as a dynamical quantum phase transition (DQPT), is a challenging task when relying solely on local observables. We exhibit that the experimentally accessible two-body Bell operator, originally designed to detect nonlocal correlations in quantum states, serves as an effective witness of DQPTs in a long-range (LR) XY spin chain subjected to a magnetic field, where the interaction strength decays as a power law. Following a sudden quench of the system parameters, the Bell operator between nearest-neighbor spins exhibits a distinct drop at the critical boundaries. In this study, we consider two quenching protocols, namely sudden quenches of the magnetic field strength and the interaction fall-off rate. This pronounced behavior defines a threshold, distinguishing intra-phase from inter-phase quenches, remaining valid regardless of the strength of long-range interactions, anisotropy, and system sizes. Comparative analyses further demonstrate that conventional classical and quantum correlators, including entanglement, fail to capture this transition during dynamics.