Work

Symmetry-Driven Thermalization via Finite de Finetti Theorems

Year: 2026

Type: article

Abstract: Thermal behavior in subsystems of closed quantum systems is commonly attributed to dynamical chaos, quantum ergodicity, canonical typicality, or the eigenstate thermalization hypothesis, suggesting a fundamentally statistical origin of thermalization. Here, we propose a potential alternative mechanism in which thermal structures emerge deterministically from symmetry considerations alone, without recourse to statistical arguments. We prove a finite de Finetti-type theorem for quantum states invariant under energy-preserving unitaries, establishing that the reduced marginals of any such invariant N-qudit state are close (both in trace distance and relative entropy) to convex mixtures of thermal product states, with explicit error bounds vanishing as N→∞. We further present an example of Lindblad dynamics whose longtime limit is invariant under energy-preserving unitaries, providing a dynamical realization of the desired symmetry class. These results imply that invariance under energy-preserving unitaries suffices as a sole fundamental, deterministic principle to enforce thermal structures.

Source: Physical Review Letters

DOI: 10.1103/df89-tdks

Authors: Uttam Singh, Nicolas J. Cerf

Institutions: International Institute of Information Technology, Hyderabad, Université Libre de Bruxelles

Language: English

Topic: Quantum many-body systems

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: ITEA, Fonds De La Recherche Scientifique - FNRS, Ministry of Electronics and Information technology, International Institute of Information Technology, Hyderabad

Awards: G2167299296, G2418290942