Discovering Local Hidden-Variable Models for Arbitrary Multipartite Entangled States and Arbitrary Measurements

Von Selzam N, Marquardt F (2025)

Publication Type: Journal article

Publication year: 2025

Journal

PRX Quantum American Physical Society

Book Volume: 6

Article Number: 020317

Journal Issue: 2

DOI: 10.1103/PRXQuantum.6.020317

Abstract

Measurement correlations in quantum systems can exhibit nonlocal behavior, a fundamental aspect of quantum mechanics with applications such as device-independent quantum information processing. However, it is in general not known which states are local and which ones are not. In particular, it remains an outstanding challenge to explicitly construct local hidden-variable (LHV) models for arbitrary multipartite entangled states. To address this, we use gradient-descent algorithms from machine learning to find LHV models that reproduce the statistics of arbitrary measurements for quantum many-body states. In contrast to previous approaches, our method employs a general ansatz, enabling it to discover LHV models for all local states. Therefore, it for example provides actual estimates for the critical noise levels at which two-qubit Werner states and three-qubit Greenberger-Horne-Zeilinger and W states become local. Furthermore, we find evidence suggesting that two-spin subsystems in the ground states of translationally invariant Hamiltonians are genuinely local, while bigger subsystems are in general not. Our method now offers a quantitative tool for determining the regimes of nonlocality in any given physical context, such as nonequilibrium, decoherence, or disorder.

Authors with CRIS profile

Florian Marquardt

Involved external institutions

Max-Planck-Institut für die Physik des Lichts (MPL) / Max Planck Institute for the Science of Light

Germany (DE)

How to cite

APA:

Von Selzam, N., & Marquardt, F. (2025). Discovering Local Hidden-Variable Models for Arbitrary Multipartite Entangled States and Arbitrary Measurements. PRX Quantum, 6(2). https://doi.org/10.1103/PRXQuantum.6.020317

MLA:

Von Selzam, Nick, and Florian Marquardt. "Discovering Local Hidden-Variable Models for Arbitrary Multipartite Entangled States and Arbitrary Measurements." PRX Quantum 6.2 (2025).

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