Approximation and Generalization Capacities of Parametrized Quantum Circuits for Functions in Sobolev Spaces

Fuente: arXiv
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Hauptverfasser: Manzano, Alberto, Dechant, David, Tura, Jordi, Dunjko, Vedran
Format: Preprint
Veröffentlicht: 2023
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author Manzano, Alberto
Dechant, David
Tura, Jordi
Dunjko, Vedran
author_facet Manzano, Alberto
Dechant, David
Tura, Jordi
Dunjko, Vedran
contents Parametrized quantum circuits (PQC) are quantum circuits which consist of both fixed and parametrized gates. In recent approaches to quantum machine learning (QML), PQCs are essentially ubiquitous and play the role analogous to classical neural networks. They are used to learn various types of data, with an underlying expectation that if the PQC is made sufficiently deep, and the data plentiful, the generalization error will vanish, and the model will capture the essential features of the distribution. While there exist results proving the approximability of square-integrable functions by PQCs under the $L^2$ distance, the approximation for other function spaces and under other distances has been less explored. In this work we show that PQCs can approximate the space of continuous functions, $p$-integrable functions and the $H^k$ Sobolev spaces under specific distances. Moreover, we develop generalization bounds that connect different function spaces and distances. These results provide a theoretical basis for different applications of PQCs, for example for solving differential equations. Furthermore, they provide us with new insight on the role of the data normalization in PQCs and of loss functions which better suit the specific needs of the users.
format Preprint
id arxiv_https___arxiv_org_abs_2307_14792
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Approximation and Generalization Capacities of Parametrized Quantum Circuits for Functions in Sobolev Spaces
Manzano, Alberto
Dechant, David
Tura, Jordi
Dunjko, Vedran
Quantum Physics
Parametrized quantum circuits (PQC) are quantum circuits which consist of both fixed and parametrized gates. In recent approaches to quantum machine learning (QML), PQCs are essentially ubiquitous and play the role analogous to classical neural networks. They are used to learn various types of data, with an underlying expectation that if the PQC is made sufficiently deep, and the data plentiful, the generalization error will vanish, and the model will capture the essential features of the distribution. While there exist results proving the approximability of square-integrable functions by PQCs under the $L^2$ distance, the approximation for other function spaces and under other distances has been less explored. In this work we show that PQCs can approximate the space of continuous functions, $p$-integrable functions and the $H^k$ Sobolev spaces under specific distances. Moreover, we develop generalization bounds that connect different function spaces and distances. These results provide a theoretical basis for different applications of PQCs, for example for solving differential equations. Furthermore, they provide us with new insight on the role of the data normalization in PQCs and of loss functions which better suit the specific needs of the users.
title Approximation and Generalization Capacities of Parametrized Quantum Circuits for Functions in Sobolev Spaces
topic Quantum Physics
url https://arxiv.org/abs/2307.14792