探测量子自旋液体中的多量子相干
Probing quantum spin liquids with multiple quantum coherences
- JILA and National Institute of Standards and Technology, University of Colorado（科罗拉多大学 JILA 与美国国家标准与技术研究院）
- Department of Physics and Center for Theory of Quantum Matter, University of Colorado（科罗拉多大学物理系与量子物质理论中心）
- Ludwig Maximilian University of Munich（慕尼黑大学）
- Arnold Sommerfeld Center for Theoretical Physics (ASC)（阿诺德·索末菲理论物理中心）
- Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文提出多量子相干（MQCs）作为探测有能隙Z2量子自旋液体的新诊断工具，通过量子蒙特卡洛模拟建立任意子激发与MQC扇区的对应，揭示任意子凝聚并区分经典与量子环气，为量子模拟器中的物相识别提供实用方法。
AI中文摘要：
量子模拟器开始制备那些在材料中难以干净实现、长期寻求的物相。然而，当这些物相的定义性质本质上是非局域的，且无法通过常规的局域测量来捕获时，识别这些物相仍然是一个重大挑战。在此，我们确立多量子相干（MQCs）作为有能隙的$\mathbb{Z}_2$量子自旋液体的相位敏感诊断工具。聚焦于扩展环面码模型，并利用大规模量子蒙特卡洛模拟，我们在基本任意子激发与不同MQC扇区的权重之间建立了直接对应关系。因此，MQCs通过特征性信号揭示了相变过程中的任意子凝聚，这些信号对使常规诊断失效的涨落保持稳健。子系统分辨的MQCs进一步提供了一种二分纠缠见证，能够区分经典环气与量子相干的闭合环气。我们开发并基准测试了一种基于绝热往返返回保真度的实用协议来提取MQCs，并表明局域相干测量保留了相变的实验可及信号。我们的结果确立了MQCs作为量子自旋液体的激发、相结构和全局约束的实用诊断工具。
英文摘要：
Quantum simulators are beginning to prepare long-sought phases of matter that remain difficult to realize cleanly in materials. Yet identifying such phases remains a major challenge when their defining properties are inherently non-local and cannot be captured by conventional local measurements. Here we establish multiple-quantum coherences (MQCs) as phase-sensitive diagnostics for gapped $\mathbb{Z}_2$ quantum spin liquids. Focusing on the extended toric code and using large-scale quantum Monte Carlo simulations, we build a direct correspondence between the elementary anyonic excitations and the weights of different MQC sectors. MQCs thereby reveal anyon condensation across the phase transitions through characteristic signatures that remain robust against fluctuations that obscure conventional diagnostics. Subsystem-resolved MQCs further provide a bipartite entanglement witness that distinguishes a classical loop gas from a quantum-coherent closed-loops gas. We develop and benchmark a practical protocol to extract MQCs based on the return fidelity of adiabatic round trips, and show that local coherence measurements retain experimentally accessible signatures of the phase transitions. Our results establish MQCs as a practical diagnostic for the excitations, phase structure and global constraints of quantum spin liquids.
