A Framework for Predicting Entanglement Spectra of Gapless Symmetry-Protected Topological States in One Dimension

Fuente: arXiv
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Autori principali: Xu, Wen-Tao, Pollmann, Frank, Knap, Michael
Natura: Preprint
Pubblicazione: 2026
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author Xu, Wen-Tao
Pollmann, Frank
Knap, Michael
author_facet Xu, Wen-Tao
Pollmann, Frank
Knap, Michael
contents The concept of gapped symmetry-protected topological (SPT) states has been generalized to gapless SPT (gSPT) states. Similar to gapped SPT states, gSPT states in one dimension exhibit universal degeneracies in their entanglement spectra. The entanglement spectra of gSPT states are further described by boundary conformal field theories, whose systematic prediction is a key open question. To address this problem, we focus on the class of gSPT states that are obtained by applying unitary SPT entanglers to trivial, critical states in one dimension. We find that the reduced density matrix of a non-trivial gSPT state can be obtained, either exactly or approximately, by applying a quantum channel to the reduced density matrix of the trivial gSPT state. This quantum channel acts only near the entanglement cut and modifies its corresponding conformal boundary condition, allowing us in turn to predict the boundary conformal field theory describing the entanglement spectra. We apply this framework to gSPT states protected by various symmetries and having different central charges, and further analyze the stability of boundary conditions of the entanglement cut. Our work thereby provides a framework for systematically analyzing and understanding the entanglement spectra of gSPT states.
format Preprint
id arxiv_https___arxiv_org_abs_2604_10128
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A Framework for Predicting Entanglement Spectra of Gapless Symmetry-Protected Topological States in One Dimension
Xu, Wen-Tao
Pollmann, Frank
Knap, Michael
Quantum Physics
Statistical Mechanics
Strongly Correlated Electrons
The concept of gapped symmetry-protected topological (SPT) states has been generalized to gapless SPT (gSPT) states. Similar to gapped SPT states, gSPT states in one dimension exhibit universal degeneracies in their entanglement spectra. The entanglement spectra of gSPT states are further described by boundary conformal field theories, whose systematic prediction is a key open question. To address this problem, we focus on the class of gSPT states that are obtained by applying unitary SPT entanglers to trivial, critical states in one dimension. We find that the reduced density matrix of a non-trivial gSPT state can be obtained, either exactly or approximately, by applying a quantum channel to the reduced density matrix of the trivial gSPT state. This quantum channel acts only near the entanglement cut and modifies its corresponding conformal boundary condition, allowing us in turn to predict the boundary conformal field theory describing the entanglement spectra. We apply this framework to gSPT states protected by various symmetries and having different central charges, and further analyze the stability of boundary conditions of the entanglement cut. Our work thereby provides a framework for systematically analyzing and understanding the entanglement spectra of gSPT states.
title A Framework for Predicting Entanglement Spectra of Gapless Symmetry-Protected Topological States in One Dimension
topic Quantum Physics
Statistical Mechanics
Strongly Correlated Electrons
url https://arxiv.org/abs/2604.10128