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arXiv 2210.02427quant-phcond-mat.dis-nncond-mat.quant-gascond-mat.str-elhep-th
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Sachdev-Ye-Kitaev模型电荷守恒扇区中平均等时观测量的算子增长的缺失

Absence of operator growth for average equal-time observables in charge-conserved sectors of the Sachdev-Ye-Kitaev model

Alessio Paviglianiti, Soumik Bandyopadhyay, Philipp Uhrich, Philipp Hauke

摘要:

量子置乱在理解封闭量子系统中的热化过程中起着重要的作用。通过这种效应,量子信息在整个系统中传播,并以非局域关联的形式隐藏起来。或者,它可以用海森堡图像中算子的复杂性和空间支持度的增加来描述,这种现象称为算子增长。在这项工作中,我们研究了无序全连接Sachdev-Ye-Kitaev(SYK)模型,我们证明了混乱是不存在的无序平均期望值的观察。详细地说,我们采用了典型的开放量子系统的形式主义表明,在平均和电荷守恒的部门内,运营商的演变是一个相对简单的方式,这是由他们的运营商的大小。该特征仅影响单次关联函数,并且特别地,它不适用于时间顺序外的干扰器,这是众所周知的,以显示加扰行为。利用这些发现,我们开发了一个累积量扩展的方法来近似的演化等时间观测。我们采用此方案,以获得适用于任意系统大小的分析结果,我们基准其有效性的精确数值。我们的研究结果揭示了SYK模型中观测量的动态结构,并提供了一个近似的数值描述,克服了标准方法对小系统的限制。

英文摘要:

Quantum scrambling plays an important role in understanding thermalization in closed quantum systems. By this effect, quantum information spreads throughout the system and becomes hidden in the form of non-local correlations. Alternatively, it can be described in terms of the increase in complexity and spatial support of operators in the Heisenberg picture, a phenomenon known as operator growth. In this work, we study the disordered fully-connected Sachdev-Ye-Kitaev (SYK) model, and we demonstrate that scrambling is absent for disorder-averaged expectation values of observables. In detail, we adopt a formalism typical of open quantum systems to show that, on average and within charge-conserved sectors, operators evolve in a relatively simple way which is governed by their operator size. This feature only affects single-time correlation functions, and in particular it does not hold for out-of-time-order correlators, which are well-known to show scrambling behavior. Making use of these findings, we develop a cumulant expansion approach to approximate the evolution of equal-time observables. We employ this scheme to obtain analytic results that apply to arbitrary system size, and we benchmark its effectiveness by exact numerics. Our findings shed light on the structure of the dynamics of observables in the SYK model, and provide an approximate numerical description that overcomes the limitation to small systems of standard methods.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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