Growth and collapse of subsystem complexity under random unitary circuits

Fuente: arXiv
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Autores principales: Haah, Jeongwan, Stanford, Douglas
Formato: Preprint
Publicado: 2025
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author Haah, Jeongwan
Stanford, Douglas
author_facet Haah, Jeongwan
Stanford, Douglas
contents For chaotic quantum dynamics modeled by random unitary circuits, we study the complexity of reduced density matrices of subsystems as a function of evolution time where the initial global state is a product pure state. The state complexity is defined as the minimum number of local quantum channels to generate a given state from a product state to a good approximation. In $1+1$d, we prove that the complexity of subsystems of length $\ell$ smaller than half grows linearly in time $T$ at least up to $T = \ell / 4$ but becomes zero after time $T = \ell /2$ in the limit of a large local dimension, while the complexity of the complementary subsystem of length larger than half grows linearly in time up to exponentially late times. Using holographic correspondence, we give some evidence that the state complexity of the smaller subsystem should actually grow linearly up to time $T = \ell/2$ and then abruptly decay to zero.
format Preprint
id arxiv_https___arxiv_org_abs_2510_18805
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Growth and collapse of subsystem complexity under random unitary circuits
Haah, Jeongwan
Stanford, Douglas
Quantum Physics
High Energy Physics - Theory
For chaotic quantum dynamics modeled by random unitary circuits, we study the complexity of reduced density matrices of subsystems as a function of evolution time where the initial global state is a product pure state. The state complexity is defined as the minimum number of local quantum channels to generate a given state from a product state to a good approximation. In $1+1$d, we prove that the complexity of subsystems of length $\ell$ smaller than half grows linearly in time $T$ at least up to $T = \ell / 4$ but becomes zero after time $T = \ell /2$ in the limit of a large local dimension, while the complexity of the complementary subsystem of length larger than half grows linearly in time up to exponentially late times. Using holographic correspondence, we give some evidence that the state complexity of the smaller subsystem should actually grow linearly up to time $T = \ell/2$ and then abruptly decay to zero.
title Growth and collapse of subsystem complexity under random unitary circuits
topic Quantum Physics
High Energy Physics - Theory
url https://arxiv.org/abs/2510.18805