Circuit Harmonic Matrices: A Spectral Framework for Quantum Machine Learning

Fuente: arXiv
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Autori principali: Campbell, Kyle James Stuart, Del Debbio, Luigi, Wallden, Petros
Natura: Preprint
Pubblicazione: 2026
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author Campbell, Kyle James Stuart
Del Debbio, Luigi
Wallden, Petros
author_facet Campbell, Kyle James Stuart
Del Debbio, Luigi
Wallden, Petros
contents Parametrised quantum circuits are a central framework for near term quantum machine learning. However, it remains challenging to determine in advance how architectural choices, such as encoding strategies, gate placement, and entangling structure, influence both the expressive capacity of the model and its trainability during optimisation. We introduce a data-agnostic framework, one requiring no knowledge of a training dataset or optimisation trajectory, that maps a broad family of circuits into a single architecture matrix built over learnable features and parameters. We show that this framework provides an explicit link between circuit structure, the correlations among learnable features, and the geometry of training kernels through the factorisation of each of these objects as quadratic forms in terms of these matrices. We show how correlations between learnable features arise from shared parameter-induced harmonics generated by non-commuting gate-observable interactions during Heisenberg back-propagation, and how these correlations are encoded directly in the architecture matrix. From this perspective, kernel structure and coefficient statistics can be reconstructed analytically from circuit design alone, without reference to a dataset or optimisation trajectory. The resulting framework makes circuit-induced structure explicit, separating architectural effects from data-dependent ones, and provides a principled foundation for analysing and comparing parametrised quantum circuits based on intrinsic, design-level signatures.
format Preprint
id arxiv_https___arxiv_org_abs_2604_04292
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Circuit Harmonic Matrices: A Spectral Framework for Quantum Machine Learning
Campbell, Kyle James Stuart
Del Debbio, Luigi
Wallden, Petros
Quantum Physics
Parametrised quantum circuits are a central framework for near term quantum machine learning. However, it remains challenging to determine in advance how architectural choices, such as encoding strategies, gate placement, and entangling structure, influence both the expressive capacity of the model and its trainability during optimisation. We introduce a data-agnostic framework, one requiring no knowledge of a training dataset or optimisation trajectory, that maps a broad family of circuits into a single architecture matrix built over learnable features and parameters. We show that this framework provides an explicit link between circuit structure, the correlations among learnable features, and the geometry of training kernels through the factorisation of each of these objects as quadratic forms in terms of these matrices. We show how correlations between learnable features arise from shared parameter-induced harmonics generated by non-commuting gate-observable interactions during Heisenberg back-propagation, and how these correlations are encoded directly in the architecture matrix. From this perspective, kernel structure and coefficient statistics can be reconstructed analytically from circuit design alone, without reference to a dataset or optimisation trajectory. The resulting framework makes circuit-induced structure explicit, separating architectural effects from data-dependent ones, and provides a principled foundation for analysing and comparing parametrised quantum circuits based on intrinsic, design-level signatures.
title Circuit Harmonic Matrices: A Spectral Framework for Quantum Machine Learning
topic Quantum Physics
url https://arxiv.org/abs/2604.04292