Lecture Notes on Replica Tensor Networks for Random Quantum Circuits

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1. Verfasser: Turkeshi, Xhek
Format: Preprint
Veröffentlicht: 2026
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author Turkeshi, Xhek
author_facet Turkeshi, Xhek
contents We present a pedagogical, hands-on tutorial on \emph{replica tensor-network} techniques for random quantum circuits. At its core, the method recasts circuit-averaged observables acting on multiple copies of the system as the contraction of a classical tensor network, equivalently the partition function of a statistical-mechanics model whose effective spins live in the commutant of the gate ensemble. The framework is general: changing the observable or the initial state modifies only the replica boundary conditions, while changing the ensemble modifies the bulk tensors. Focusing on quantum-information diagnostics, from metrics of wavefunction spreadings to entanglement quantifiers, we illustrate the approach in both clean and noisy random unitary circuits. We then briefly explain how the methodology extends to other ensembles, such as orthogonal or Clifford circuits. The lecture notes are accompanied by \texttt{ReplicaTN}, a self-contained C++/Python library and pedagogical notebooks.
format Preprint
id arxiv_https___arxiv_org_abs_2605_11150
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Lecture Notes on Replica Tensor Networks for Random Quantum Circuits
Turkeshi, Xhek
Quantum Physics
Statistical Mechanics
We present a pedagogical, hands-on tutorial on \emph{replica tensor-network} techniques for random quantum circuits. At its core, the method recasts circuit-averaged observables acting on multiple copies of the system as the contraction of a classical tensor network, equivalently the partition function of a statistical-mechanics model whose effective spins live in the commutant of the gate ensemble. The framework is general: changing the observable or the initial state modifies only the replica boundary conditions, while changing the ensemble modifies the bulk tensors. Focusing on quantum-information diagnostics, from metrics of wavefunction spreadings to entanglement quantifiers, we illustrate the approach in both clean and noisy random unitary circuits. We then briefly explain how the methodology extends to other ensembles, such as orthogonal or Clifford circuits. The lecture notes are accompanied by \texttt{ReplicaTN}, a self-contained C++/Python library and pedagogical notebooks.
title Lecture Notes on Replica Tensor Networks for Random Quantum Circuits
topic Quantum Physics
Statistical Mechanics
url https://arxiv.org/abs/2605.11150