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  • Letter
  • Open Access

Exact quench dynamics from thermal pure quantum states

Hui-Huang Chen*

  • *Contact author: chenhh@jxnu.edu.cn
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Phys. Rev. B 114, L020302 – Published 8 July, 2026

DOI: https://doi.org/10.1103/899k-yxpj

Abstract

We present an exact solution for entanglement entropy for the real-time dynamics following a quench from a thermal pure quantum (TPQ) state in a free-fermion system. In contrast to the usual linear growth and saturation behavior, the entanglement entropy exhibits a characteristic double-plateau structure. We establish this behavior through three complementary approaches: an exact conformal field theory calculation on the Klein bottle, finite-size Gaussian-state simulations, and a quasiparticle picture that becomes quantitatively accurate in the scaling regime.

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Phys. Rev. B 114, L020302– Published 8 July, 2026
  • Received 8 October 2025
  • Revised 28 May 2026
  • Accepted 8 June 2026
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