Embedding of Tree Tensor Networks into Shallow Quantum Circuits

Fuente: arXiv
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Main Authors: Sugawara, Shota, Inomata, Kazuki, Okubo, Tsuyoshi, Todo, Synge
Format: Preprint
Published: 2025
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author Sugawara, Shota
Inomata, Kazuki
Okubo, Tsuyoshi
Todo, Synge
author_facet Sugawara, Shota
Inomata, Kazuki
Okubo, Tsuyoshi
Todo, Synge
contents Variational Quantum Algorithms (VQAs) are being highlighted as key quantum algorithms for demonstrating quantum advantage on Noisy Intermediate-Scale Quantum (NISQ) devices, which are limited to executing shallow quantum circuits because of noise. However, the barren plateau problem, where the gradient of the loss function becomes exponentially small with system size, hinders this goal. Recent studies suggest that embedding tensor networks into quantum circuits and initializing the parameters can avoid the barren plateau. Yet, embedding tensor networks into quantum circuits is generally difficult, and methods have been limited to the simplest structure, Matrix Product States (MPSs). This study proposes a method to embed Tree Tensor Networks (TTNs), characterized by their hierarchical structure, into shallow quantum circuits. TTNs are suitable for representing two-dimensional systems and systems with long-range correlations, which MPSs are inadequate for representing. Our numerical results show that embedding TTNs provides better initial quantum circuits than MPS. Additionally, our method has a practical computational complexity, making it applicable to a wide range of TTNs. This study is expected to extend the application of VQAs to two-dimensional systems and those with long-range correlations, which have been challenging to utilize.
format Preprint
id arxiv_https___arxiv_org_abs_2501_18856
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Embedding of Tree Tensor Networks into Shallow Quantum Circuits
Sugawara, Shota
Inomata, Kazuki
Okubo, Tsuyoshi
Todo, Synge
Quantum Physics
Variational Quantum Algorithms (VQAs) are being highlighted as key quantum algorithms for demonstrating quantum advantage on Noisy Intermediate-Scale Quantum (NISQ) devices, which are limited to executing shallow quantum circuits because of noise. However, the barren plateau problem, where the gradient of the loss function becomes exponentially small with system size, hinders this goal. Recent studies suggest that embedding tensor networks into quantum circuits and initializing the parameters can avoid the barren plateau. Yet, embedding tensor networks into quantum circuits is generally difficult, and methods have been limited to the simplest structure, Matrix Product States (MPSs). This study proposes a method to embed Tree Tensor Networks (TTNs), characterized by their hierarchical structure, into shallow quantum circuits. TTNs are suitable for representing two-dimensional systems and systems with long-range correlations, which MPSs are inadequate for representing. Our numerical results show that embedding TTNs provides better initial quantum circuits than MPS. Additionally, our method has a practical computational complexity, making it applicable to a wide range of TTNs. This study is expected to extend the application of VQAs to two-dimensional systems and those with long-range correlations, which have been challenging to utilize.
title Embedding of Tree Tensor Networks into Shallow Quantum Circuits
topic Quantum Physics
url https://arxiv.org/abs/2501.18856