论文标题

动态量子相变的局部测量

Local measures of dynamical quantum phase transitions

论文作者

Halimeh, Jad C., Trapin, Daniele, Van Damme, Maarten, Heyl, Markus

论文摘要

近年来,动态量子相变(DQPTS)已成为一种有用的理论概念,可以表征量子物质的非平衡状态。 dqpts在\ textit {有效的自由能} $λ(t)$中以奇异的行为为特征,但是,这是一种全球措施,使其实验性或理论检测一般具有挑战性。我们引入了两种局部措施来检测DQPT,其优势比完全有效的自由能提供了更少的资源。第一个称为\ textIt {真实本地}有效的自由能$λ_m(t)$,在实际空间中定义,因此适用于直接可访问局部解决测量值的系统,例如涉及Rydberg Atoms或捕获离子的量子模拟器实验。我们测试了$λ_m(t)$ in Ising链中,具有最近的邻居和幂律相互作用,发现此措施允许提取DQPT的通用临界行为。我们介绍的第二个措施是\ textIt {动量 - 局部}有效的自由能$λ_K(t)$,它的目标是在动量分辨量更自然地访问的系统上,例如在超低原子中的飞行时间测量。在存在弱相互作用的情况下,我们为Kitaev链(用于拓扑量子物质的范式系统)基准了$λ_K(T)$。我们引入的有效自由能的局部措施可以进一步促进现代量子模拟器实验中DQPT的检测。

In recent years, dynamical quantum phase transitions (DQPTs) have emerged as a useful theoretical concept to characterize nonequilibrium states of quantum matter. DQPTs are marked by singular behavior in an \textit{effective free energy} $λ(t)$, which, however, is a global measure, making its experimental or theoretical detection challenging in general. We introduce two local measures for the detection of DQPTs with the advantage of requiring fewer resources than the full effective free energy. The first, called the \textit{real-local} effective free energy $λ_M(t)$, is defined in real space and is therefore suitable for systems where locally resolved measurements are directly accessible such as in quantum-simulator experiments involving Rydberg atoms or trapped ions. We test $λ_M(t)$ in Ising chains with nearest-neighbor and power-law interactions, and find that this measure allows extraction of the universal critical behavior of DQPTs. The second measure we introduce is the \textit{momentum-local} effective free energy $λ_k(t)$, which is targeted at systems where momentum-resolved quantities are more naturally accessible, such as through time-of-flight measurements in ultracold atoms. We benchmark $λ_k(t)$ for the Kitaev chain, a paradigmatic system for topological quantum matter, in the presence of weak interactions. Our introduced local measures for effective free energies can further facilitate the detection of DQPTs in modern quantum-simulator experiments.

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