Quantum Deep Learning: A Comprehensive Review
Abstract
Quantum deep learning (QDL) explores the use of both quantum and quantum-inspired resources to determine when deep learning's core capabilities, such as expressivity, generalization, and scalability, can be enhanced based on specific resource constraints. Distinct from broader quantum machine learning, QDL emphasizes compositional depth at the pipeline level and the integration of quantum or quantum-inspired components within end-to-end workflows. This review provides an operational definition of QDL and introduces a taxonomy comprising four primary paradigms: hybrid quantum-classical models, quantum deep neural networks, quantum algorithms for deep learning primitives, and quantum-inspired classical algorithms. Theoretical principles are connected to advanced architectures, software toolchains, and experimental demonstrations across superconducting, trapped-ion, photonic, semiconductor spin, and neutral-atom systems, as well as quantum annealers. Claims of quantum advantage are critically assessed by distinguishing provable complexity-theoretic separations from empirical observations. The analysis characterizes trade-offs between model expressivity, trainability, and classical simulability, while systematically detailing the bottlenecks imposed by optimization landscapes, input-output access models, and hardware constraints. Applications are surveyed in domains encompassing image classification, natural language processing, scientific discovery, quantum data processing, and quantum optimal control, underscoring fair benchmarking against optimized classical counterparts and a comprehensive assessment of resource requirements. This review serves as a tutorial entry point for graduate students while guiding readers to specialized literature. It concludes with a verification-aware roadmap to transition QDL from near-term demonstrations to scalable and fault-tolerant implementations.
Authors 13
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Affiliation as printed
Institute for Quantum Computing Analytics (PGI-12) , Forschungszentrum Jülich , 52425 Jülich , Germany
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Affiliation as printed
Institute of Artificial Intelligence , Hefei Comprehensive National Science Center , Hefei , Anhui , 230088 , P. R. China
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Fraunhofer Institute for Manufacturing Engineering and Automation
Affiliation as printed
Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) , Nobelstrasse 12 , Stuttgart 70569 , Germany
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Affiliation as printed
Heilbronn University of Applied Sciences , Max-Planck-Str. 39 , 74081 Heilbronn , Germany
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Affiliation as printed
Helmholtz AI , Research Centre Jülich , Jülich , Germany
Institute of Neuroscience and Medicine (INM-1) , Research Centre Jülich , Jülich , Germany
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University of Bonn · Ludwig-Maximilians-Universität München
Affiliation as printed
Lichtenberg Group for History and Philosophy of Physics , University of Bonn , Bonn , Germany
Munich Center for Mathematical Philosophy , Ludwig Maximilian University of Munich , Munich , Germany
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Ferdinand-Braun-Institut · Humboldt-Universität zu Berlin
Affiliation as printed
Ferdinand-Braun-Institut (FBH) , Gustav-Kirchoff-Straße 4 , 12489 Berlin , Germany
Institut für Physik and Center for the Science of Materials Berlin (CSMB) Adlershof , Humboldt-Universität zu Berlin , Newtonstrß 15 , 12489 Berlin , Germany
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Affiliation as printed
Institute for Automation of Complex Power Systems , RWTH Aachen University , Aachen , Germany
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Ferdinand-Braun-Institut · Humboldt-Universität zu Berlin
Affiliation as printed
Ferdinand-Braun-Institut (FBH) , Gustav-Kirchoff-Straße 4 , 12489 Berlin , Germany
Institut für Physik and Center for the Science of Materials Berlin (CSMB) Adlershof , Humboldt-Universität zu Berlin , Newtonstrß 15 , 12489 Berlin , Germany
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Forschungszentrum Jülich · Jülich Supercomputing Centre · FH Aachen
Affiliation as printed
Faculty of Medical Engineering and Technomathematics , University of Applied Sciences Aachen , 52428 Jülich , Germany
Jülich Supercomputing Centre , Forschungszentrum Jülich , 52425 Jülich , Germany
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Forschungszentrum Jülich · Saarland University
Affiliation as printed
Institute for Quantum Computing Analytics (PGI-12) , Forschungszentrum Jülich , 52425 Jülich , Germany
Theoretical Physics , Saarland University , 66123 Saarbrücken , Germany