arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1709.08784cond-mat.stat-mechcond-mat.str-elhep-thquant-ph
收藏

混沌本征态的Renyi熵

Renyi Entropy of Chaotic Eigenstates

Tsung-Cheng Lu, Tarun Grover

摘要:

利用遍历性理论,推导出了对应于混沌多体哈密顿量有限能量密度本征态的Renyi纠缠熵的解析表达式.该表达式是态密度的普适函数,即使当子系统是整个系统的有限部分时也是有效的--在这种情况下,约化的密度矩阵不是热的。我们发现,在热力学极限下,只有冯诺伊曼熵密度与子系统与总系统之比$V_A/V$无关,而Renyi熵密度非线性地依赖于$V_A/V$。令人惊讶的是,Renyi熵$S_n$的$n > 1$是凸函数的子系统的大小,与体积定律系数取决于$V_A/V$,并超过了热混合状态在相同的能量密度。我们提供了两个不同的论据来支持我们的结果:第一个依赖于多体版本的Berry公式的混沌量子力学系统,是密切相关的本征态热化假设。第二个论点依赖于这样的假设,即对于一个子系统中的固定能量,能量守恒允许的其补充中的所有状态都是同样可能的。我们对量子自旋链哈密顿量进行了精确对角化研究,以检验我们的分析预测,并发现很好的一致性。

英文摘要:

Using arguments built on ergodicity, we derive an analytical expression for the Renyi entanglement entropies corresponding to the finite-energy density eigenstates of chaotic many-body Hamiltonians. The expression is a universal function of the density of states and is valid even when the subsystem is a finite fraction of the total system - a regime in which the reduced density matrix is not thermal. We find that in the thermodynamic limit, only the von Neumann entropy density is independent of the subsystem to the total system ratio $V_A/V$, while the Renyi entropy densities depend non-linearly on $V_A/V$. Surprisingly, Renyi entropies $S_n$ for $n > 1$ are convex functions of the subsystem size, with a volume law coefficient that depends on $V_A/V$, and exceeds that of a thermal mixed state at the same energy density. We provide two different arguments to support our results: the first one relies on a many-body version of Berry's formula for chaotic quantum mechanical systems, and is closely related to eigenstate thermalization hypothesis. The second argument relies on the assumption that for a fixed energy in a subsystem, all states in its complement allowed by the energy conservation are equally likely. We perform Exact Diagonalization study on quantum spin-chain Hamiltonians to test our analytical predictions, and find good agreement.

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。

↑