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arXiv 2204.08147quant-phcond-mat.str-elcs.NAmath.NA
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强耦合开放量子系统平衡约化密度矩阵的数值计算

Numerical computation of the equilibrium-reduced density matrix for strongly coupled open quantum systems

Tyler Chen, Yu-Chen Cheng

摘要:

我们描述了一个数值算法近似的平衡约化的密度矩阵和有效的(平均力)的哈密顿量为一组系统的自旋强烈耦合到一组浴自旋时,整个系统(系统+浴)是在典型的热平衡弱耦合的“超级浴”。我们的方法是现在标准的典型算法计算裸量子系统的可观测量的量子期望值通过迹估计和Krylov子空间方法的推广。特别是,我们的算法利用的事实,即约化系统密度,当浴在一个给定的随机状态下测量,往往集中在相应的热力学平均约化系统密度。理论误差分析和数值实验验证了算法的准确性。进一步的数值实验证明了我们的方法的应用潜力,包括量子相变和纠缠熵的长程相互作用系统的研究。

英文摘要:

We describe a numerical algorithm for approximating the equilibrium-reduced density matrix and the effective (mean force) Hamiltonian for a set of system spins coupled strongly to a set of bath spins when the total system (system+bath) is held in canonical thermal equilibrium by weak coupling with a "super-bath". Our approach is a generalization of now standard typicality algorithms for computing the quantum expectation value of observables of bare quantum systems via trace estimators and Krylov subspace methods. In particular, our algorithm makes use of the fact that the reduced system density, when the bath is measured in a given random state, tends to concentrate about the corresponding thermodynamic averaged reduced system density. Theoretical error analysis and numerical experiments are given to validate the accuracy of our algorithm. Further numerical experiments demonstrate the potential of our approach for applications including the study of quantum phase transitions and entanglement entropy for long-range interaction systems.

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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