Thermal pure states for systems with antiunitary symmetries and their tensor network representations

Thermal pure state algorithms, which employ pure quantum states representing thermal equilibrium states instead of statistical ensembles, are useful both for numerical simulations and for theoretical analysis of thermal states. However, their inherently large entanglement makes it difficult to repre...

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Main Author: Yasushi Yoneta
Format: Article
Language:English
Published: American Physical Society 2024-12-01
Series:Physical Review Research
Online Access:http://doi.org/10.1103/PhysRevResearch.6.L042062
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author Yasushi Yoneta
author_facet Yasushi Yoneta
author_sort Yasushi Yoneta
collection DOAJ
description Thermal pure state algorithms, which employ pure quantum states representing thermal equilibrium states instead of statistical ensembles, are useful both for numerical simulations and for theoretical analysis of thermal states. However, their inherently large entanglement makes it difficult to represent efficiently and limits their use in analyzing large systems. Here we propose a tensor network algorithm for constructing thermal pure states for systems with certain antiunitary symmetries, such as time-reversal or complex-conjugate symmetry. Our method utilizes thermal pure states that, while exhibiting volume-law entanglement, can be mapped to tensor network states through simple transformations. Furthermore, our approach does not rely on random sampling and thus avoids statistical uncertainty. Moreover, we can compute not only thermal expectation values of local observables but also thermodynamic quantities. We demonstrate the validity and utility of our method by applying it to the one-dimensional XY model and the two-dimensional Ising model on a triangular lattice. Our results suggest a class of variational wave functions for volume-law states that are not limited to thermal equilibrium states.
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spelling doaj-art-b685a08040124fb4a9301ea26368df812025-08-20T02:38:49ZengAmerican Physical SocietyPhysical Review Research2643-15642024-12-0164L04206210.1103/PhysRevResearch.6.L042062Thermal pure states for systems with antiunitary symmetries and their tensor network representationsYasushi YonetaThermal pure state algorithms, which employ pure quantum states representing thermal equilibrium states instead of statistical ensembles, are useful both for numerical simulations and for theoretical analysis of thermal states. However, their inherently large entanglement makes it difficult to represent efficiently and limits their use in analyzing large systems. Here we propose a tensor network algorithm for constructing thermal pure states for systems with certain antiunitary symmetries, such as time-reversal or complex-conjugate symmetry. Our method utilizes thermal pure states that, while exhibiting volume-law entanglement, can be mapped to tensor network states through simple transformations. Furthermore, our approach does not rely on random sampling and thus avoids statistical uncertainty. Moreover, we can compute not only thermal expectation values of local observables but also thermodynamic quantities. We demonstrate the validity and utility of our method by applying it to the one-dimensional XY model and the two-dimensional Ising model on a triangular lattice. Our results suggest a class of variational wave functions for volume-law states that are not limited to thermal equilibrium states.http://doi.org/10.1103/PhysRevResearch.6.L042062
spellingShingle Yasushi Yoneta
Thermal pure states for systems with antiunitary symmetries and their tensor network representations
Physical Review Research
title Thermal pure states for systems with antiunitary symmetries and their tensor network representations
title_full Thermal pure states for systems with antiunitary symmetries and their tensor network representations
title_fullStr Thermal pure states for systems with antiunitary symmetries and their tensor network representations
title_full_unstemmed Thermal pure states for systems with antiunitary symmetries and their tensor network representations
title_short Thermal pure states for systems with antiunitary symmetries and their tensor network representations
title_sort thermal pure states for systems with antiunitary symmetries and their tensor network representations
url http://doi.org/10.1103/PhysRevResearch.6.L042062
work_keys_str_mv AT yasushiyoneta thermalpurestatesforsystemswithantiunitarysymmetriesandtheirtensornetworkrepresentations