Efficient computation of average subsystem Bures distance in transverse field Ising chain

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Hauptverfasser: Guo, Zhouhao, Rajabpour, M. A., Zhang, Jiaju
Format: Preprint
Veröffentlicht: 2025
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author Guo, Zhouhao
Rajabpour, M. A.
Zhang, Jiaju
author_facet Guo, Zhouhao
Rajabpour, M. A.
Zhang, Jiaju
contents The average subsystem trace distance has been proposed as an indicator of quantum many-body chaos and integrability. In integrable systems, evaluating the trace distance faces two challenges: the computational cost for large systems and ambiguities in defining and ordering eigenstates. In this paper, we calculate the average subsystem Bures distance in the spin-1/2 transverse-field Ising chain. We develop an efficient algorithm to evaluate the Bures distance between two Gaussian states, which allows us to access larger system sizes. To address the degeneracy issue, we consider simultaneous eigenstates of all local conserved charges and use these charges to systematically order degenerate states. The results align with the conjectured linear increase with subsystem size. We demonstrate that the distinct scaling behaviors of the average subsystem trace and Bures distances in chaotic versus integrable systems stem from discontinuities of local conserved charges across the spectrum in integrable systems. Additionally, we investigate the average subsystem distances between random pure Gaussian states but do not observe a linear increase.
format Preprint
id arxiv_https___arxiv_org_abs_2508_09417
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Efficient computation of average subsystem Bures distance in transverse field Ising chain
Guo, Zhouhao
Rajabpour, M. A.
Zhang, Jiaju
Quantum Physics
Statistical Mechanics
High Energy Physics - Theory
The average subsystem trace distance has been proposed as an indicator of quantum many-body chaos and integrability. In integrable systems, evaluating the trace distance faces two challenges: the computational cost for large systems and ambiguities in defining and ordering eigenstates. In this paper, we calculate the average subsystem Bures distance in the spin-1/2 transverse-field Ising chain. We develop an efficient algorithm to evaluate the Bures distance between two Gaussian states, which allows us to access larger system sizes. To address the degeneracy issue, we consider simultaneous eigenstates of all local conserved charges and use these charges to systematically order degenerate states. The results align with the conjectured linear increase with subsystem size. We demonstrate that the distinct scaling behaviors of the average subsystem trace and Bures distances in chaotic versus integrable systems stem from discontinuities of local conserved charges across the spectrum in integrable systems. Additionally, we investigate the average subsystem distances between random pure Gaussian states but do not observe a linear increase.
title Efficient computation of average subsystem Bures distance in transverse field Ising chain
topic Quantum Physics
Statistical Mechanics
High Energy Physics - Theory
url https://arxiv.org/abs/2508.09417