Spectral Phase Encoding for Quantum Kernel Methods

Fuente: arXiv
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Auteurs principaux: Gómez, Pablo Herrero, Morenilla, Antonio Jimeno, Muñoz-Hernández, David, Mora, Higinio Mora
Format: Preprint
Publié: 2026
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author Gómez, Pablo Herrero
Morenilla, Antonio Jimeno
Muñoz-Hernández, David
Mora, Higinio Mora
author_facet Gómez, Pablo Herrero
Morenilla, Antonio Jimeno
Muñoz-Hernández, David
Mora, Higinio Mora
contents Quantum kernel methods are promising for near-term quantum ma- chine learning, yet their behavior under data corruption remains insuf- ficiently understood. We analyze how quantum feature constructions degrade under controlled additive noise. We introduce Spectral Phase Encoding (SPE), a hybrid construc- tion combining a discrete Fourier transform (DFT) front-end with a diagonal phase-only embedding aligned with the geometry of diagonal quantum maps. Within a unified framework, we compare QK-DFT against alternative quantum variants (QK-PCA, QK-RP) and classi- cal SVM baselines under identical clean-data hyperparameter selection, quantifying robustness via dataset fixed-effects regression with wild cluster bootstrap inference across heterogeneous real-world datasets. Across the quantum family, DFT-based preprocessing yields the smallest degradation rate as noise increases, with statistically sup- ported slope differences relative to PCA and RP. Compared to classical baselines, QK-DFT shows degradation comparable to linear SVM and more stable than RBF SVM under matched tuning. Hardware exper- iments confirm that SPE remains executable and numerically stable for overlap estimation. These results indicate that robustness in quan- tum kernels depends critically on structure-aligned preprocessing and its interaction with diagonal embeddings, supporting a robustness-first perspective for NISQ-era quantum machine learning.
format Preprint
id arxiv_https___arxiv_org_abs_2602_19644
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Spectral Phase Encoding for Quantum Kernel Methods
Gómez, Pablo Herrero
Morenilla, Antonio Jimeno
Muñoz-Hernández, David
Mora, Higinio Mora
Machine Learning
Quantum Physics
Quantum kernel methods are promising for near-term quantum ma- chine learning, yet their behavior under data corruption remains insuf- ficiently understood. We analyze how quantum feature constructions degrade under controlled additive noise. We introduce Spectral Phase Encoding (SPE), a hybrid construc- tion combining a discrete Fourier transform (DFT) front-end with a diagonal phase-only embedding aligned with the geometry of diagonal quantum maps. Within a unified framework, we compare QK-DFT against alternative quantum variants (QK-PCA, QK-RP) and classi- cal SVM baselines under identical clean-data hyperparameter selection, quantifying robustness via dataset fixed-effects regression with wild cluster bootstrap inference across heterogeneous real-world datasets. Across the quantum family, DFT-based preprocessing yields the smallest degradation rate as noise increases, with statistically sup- ported slope differences relative to PCA and RP. Compared to classical baselines, QK-DFT shows degradation comparable to linear SVM and more stable than RBF SVM under matched tuning. Hardware exper- iments confirm that SPE remains executable and numerically stable for overlap estimation. These results indicate that robustness in quan- tum kernels depends critically on structure-aligned preprocessing and its interaction with diagonal embeddings, supporting a robustness-first perspective for NISQ-era quantum machine learning.
title Spectral Phase Encoding for Quantum Kernel Methods
topic Machine Learning
Quantum Physics
url https://arxiv.org/abs/2602.19644