Learning transitions in classical Ising models and deformed toric codes

Fuente: arXiv
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Main Authors: Pütz, Malte, Garratt, Samuel J., Nishimori, Hidetoshi, Trebst, Simon, Zhu, Guo-Yi
Format: Preprint
Published: 2025
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author Pütz, Malte
Garratt, Samuel J.
Nishimori, Hidetoshi
Trebst, Simon
Zhu, Guo-Yi
author_facet Pütz, Malte
Garratt, Samuel J.
Nishimori, Hidetoshi
Trebst, Simon
Zhu, Guo-Yi
contents Conditional probability distributions describe the effect of learning an initially unknown classical state through Bayesian inference. Here we demonstrate the existence of a \textit{learning transition}, having signatures in the long distance behavior of conditional correlation functions, in the two-dimensional classical Ising model. This transition, which arises when learning local energy densities, extends all the way from the infinite-temperature paramagnetic state down to the thermal critical state. The intersection of the line of learning transitions and the thermal Ising transition is a new tricritical point. Our model for learning also exactly describes the effects of weak measurements on ground states of frustration-free quantum Hamiltonians, which interpolate between the toric code and a paramagnet. Notably, the location of the above tricritical point implies that the quantum memory defined by the degenerate ground states in the topological phase is robust to weak measurement, even when the initial state is arbitrarily close to the quantum phase transition separating topological and trivial phases. Our analysis uses a replica field theory combined with the renormalization group, and we chart out the phase diagram using a combination of tensor network and Monte Carlo techniques. Our methods can be extended to study the more general effects of learning on both classical and quantum states. The learning induced critical states can be realized in classical or quantum devices.
format Preprint
id arxiv_https___arxiv_org_abs_2504_12385
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Learning transitions in classical Ising models and deformed toric codes
Pütz, Malte
Garratt, Samuel J.
Nishimori, Hidetoshi
Trebst, Simon
Zhu, Guo-Yi
Statistical Mechanics
Disordered Systems and Neural Networks
Quantum Physics
Conditional probability distributions describe the effect of learning an initially unknown classical state through Bayesian inference. Here we demonstrate the existence of a \textit{learning transition}, having signatures in the long distance behavior of conditional correlation functions, in the two-dimensional classical Ising model. This transition, which arises when learning local energy densities, extends all the way from the infinite-temperature paramagnetic state down to the thermal critical state. The intersection of the line of learning transitions and the thermal Ising transition is a new tricritical point. Our model for learning also exactly describes the effects of weak measurements on ground states of frustration-free quantum Hamiltonians, which interpolate between the toric code and a paramagnet. Notably, the location of the above tricritical point implies that the quantum memory defined by the degenerate ground states in the topological phase is robust to weak measurement, even when the initial state is arbitrarily close to the quantum phase transition separating topological and trivial phases. Our analysis uses a replica field theory combined with the renormalization group, and we chart out the phase diagram using a combination of tensor network and Monte Carlo techniques. Our methods can be extended to study the more general effects of learning on both classical and quantum states. The learning induced critical states can be realized in classical or quantum devices.
title Learning transitions in classical Ising models and deformed toric codes
topic Statistical Mechanics
Disordered Systems and Neural Networks
Quantum Physics
url https://arxiv.org/abs/2504.12385