Expressivity Limits of Quantum Reservoir Computing

Fuente: arXiv
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Autori principali: Schütte, Nils-Erik, Götting, Niclas, Müntinga, Hauke, List, Meike, Brunner, Daniel, Gies, Christopher
Natura: Preprint
Pubblicazione: 2025
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author Schütte, Nils-Erik
Götting, Niclas
Müntinga, Hauke
List, Meike
Brunner, Daniel
Gies, Christopher
author_facet Schütte, Nils-Erik
Götting, Niclas
Müntinga, Hauke
List, Meike
Brunner, Daniel
Gies, Christopher
contents We investigate the fundamental expressivity limits of quantum reservoir computing (QRC) by establishing a formal connection to parametrized quantum circuit quantum machine learning (PQC-QML). We analytically prove, and numerically corroborate, that in QRC the number of orthogonal non-linear functions that can be generated from classical data is bounded linearly by the number of input encoding gates, independent of the reservoir's Hilbert space size. This finding applies across both physical and gate-based reservoir implementations using typical single-qubit input rotation schemes. Our results challenge the common assumption that exponential Hilbert space scaling confers a corresponding computational advantage in QRC, and demonstrate that true quantum benefit will require either more sophisticated, potentially multi-qubit, input schemes or quantum-native input data. These insights lay new groundwork for the design and evaluation of future QRC hardware and algorithms.
format Preprint
id arxiv_https___arxiv_org_abs_2501_15528
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Expressivity Limits of Quantum Reservoir Computing
Schütte, Nils-Erik
Götting, Niclas
Müntinga, Hauke
List, Meike
Brunner, Daniel
Gies, Christopher
Quantum Physics
We investigate the fundamental expressivity limits of quantum reservoir computing (QRC) by establishing a formal connection to parametrized quantum circuit quantum machine learning (PQC-QML). We analytically prove, and numerically corroborate, that in QRC the number of orthogonal non-linear functions that can be generated from classical data is bounded linearly by the number of input encoding gates, independent of the reservoir's Hilbert space size. This finding applies across both physical and gate-based reservoir implementations using typical single-qubit input rotation schemes. Our results challenge the common assumption that exponential Hilbert space scaling confers a corresponding computational advantage in QRC, and demonstrate that true quantum benefit will require either more sophisticated, potentially multi-qubit, input schemes or quantum-native input data. These insights lay new groundwork for the design and evaluation of future QRC hardware and algorithms.
title Expressivity Limits of Quantum Reservoir Computing
topic Quantum Physics
url https://arxiv.org/abs/2501.15528