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arXiv 2108.09391quant-phcond-mat.quant-gas
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来自量子探针的混沌假信号

False signals of chaos from quantum probes

W. Kirkby, D. H. J. O'Dell, J. Mumford

摘要:

我们证明,两个时间的关联函数,这是广义的时间有序的振荡器(OTOC),可以显示“假旗”的混乱表现出随机矩阵理论预测的行为,即使在一个系统的经典规则的动态。特别是,我们分析了一个系统的玻色子被困在一个双阱势和探测的量子点,这是耦合到玻色子色散。这是一个可积系统(既可以看作是独立的部分,也可以看作是整体)。尽管连续的时间演化所产生的实际的哈密顿量,我们发现,n倍的两个时间关联函数的探头描述了一个有效的频闪或Floquet动力学,从而出现的玻色子交替驱动两个不同的非交换哈密顿量的方式让人想起的Trottered的时间演化发生在数字量子模拟。这种有效动力学的经典极限可以有一个非零的李雅普诺夫指数,而有效水平的统计和返回概率显示传统的签名混沌行为。与最近的其他几项研究一致,这项工作强调了这样一个事实,即必须谨慎解释OTOC的行为及其概括。

英文摘要:

We demonstrate that two-time correlation functions, which are generalizations of out-of-time-ordered correlators (OTOCs), can show 'false-flags' of chaos by exhibiting behaviour predicted by random matrix theory even in a system with classically regular dynamics. In particular, we analyze a system of bosons trapped in a double-well potential and probed by a quantum dot which is coupled to the bosons dispersively. This is an integrable system (considered both as separate parts and in total). Despite the continuous time evolution generated by the actual Hamiltonian, we find that the n-fold two-time correlation function for the probe describes an effective stroboscopic or Floquet dynamics whereby the bosons appear to be alternately driven by two different non-commuting Hamiltonians in a manner reminiscent of the Trotterized time evolution that occurs in digital quantum simulation. The classical limit of this effective dynamics can have a nonzero Lyapunov exponent, while the effective level statistics and return probability show traditional signatures of chaotic behaviour. In line with several other recent studies, this work highlights the fact that the behavior of OTOCs and their generalizations must be interpreted with some care.

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