Universality of physical neural networks with multivariate nonlinearity

Fuente: arXiv
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Autori principali: Savinson, Benjamin, Norris, David J., Mishra, Siddhartha, Lanthaler, Samuel
Natura: Preprint
Pubblicazione: 2025
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author Savinson, Benjamin
Norris, David J.
Mishra, Siddhartha
Lanthaler, Samuel
author_facet Savinson, Benjamin
Norris, David J.
Mishra, Siddhartha
Lanthaler, Samuel
contents The enormous energy demand of artificial intelligence is driving the development of alternative hardware for deep learning. Physical neural networks try to exploit physical systems to perform machine learning more efficiently. In particular, optical systems can calculate with light using negligible energy. While their computational capabilities were long limited by the linearity of optical materials, nonlinear computations have recently been demonstrated through modified input encoding. Despite this breakthrough, our inability to determine if physical neural networks can learn arbitrary relationships between data -- a key requirement for deep learning known as universality -- hinders further progress. Here we present a fundamental theorem that establishes a universality condition for physical neural networks. It provides a powerful mathematical criterion that imposes device constraints, detailing how inputs should be encoded in the tunable parameters of the physical system. Based on this result, we propose a scalable architecture using free-space optics that is provably universal and achieves high accuracy on image classification tasks. Further, by combining the theorem with temporal multiplexing, we present a route to potentially huge effective system sizes in highly practical but poorly scalable on-chip photonic devices. Our theorem and scaling methods apply beyond optical systems and inform the design of a wide class of universal, energy-efficient physical neural networks, justifying further efforts in their development.
format Preprint
id arxiv_https___arxiv_org_abs_2509_05420
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Universality of physical neural networks with multivariate nonlinearity
Savinson, Benjamin
Norris, David J.
Mishra, Siddhartha
Lanthaler, Samuel
Optics
Artificial Intelligence
Classical Physics
Computational Physics
The enormous energy demand of artificial intelligence is driving the development of alternative hardware for deep learning. Physical neural networks try to exploit physical systems to perform machine learning more efficiently. In particular, optical systems can calculate with light using negligible energy. While their computational capabilities were long limited by the linearity of optical materials, nonlinear computations have recently been demonstrated through modified input encoding. Despite this breakthrough, our inability to determine if physical neural networks can learn arbitrary relationships between data -- a key requirement for deep learning known as universality -- hinders further progress. Here we present a fundamental theorem that establishes a universality condition for physical neural networks. It provides a powerful mathematical criterion that imposes device constraints, detailing how inputs should be encoded in the tunable parameters of the physical system. Based on this result, we propose a scalable architecture using free-space optics that is provably universal and achieves high accuracy on image classification tasks. Further, by combining the theorem with temporal multiplexing, we present a route to potentially huge effective system sizes in highly practical but poorly scalable on-chip photonic devices. Our theorem and scaling methods apply beyond optical systems and inform the design of a wide class of universal, energy-efficient physical neural networks, justifying further efforts in their development.
title Universality of physical neural networks with multivariate nonlinearity
topic Optics
Artificial Intelligence
Classical Physics
Computational Physics
url https://arxiv.org/abs/2509.05420