Maximum Entropy Principle in Deep Thermalization and in Hilbert-Space Ergodicity

We report universal statistical properties displayed by ensembles of pure states that naturally emerge in quantum many-body systems. Specifically, two classes of state ensembles are considered: those formed by (i) the temporal trajectory of a quantum state under unitary evolution or (ii) the quantum...

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Main Authors: Daniel K. Mark, Federica Surace, Andreas Elben, Adam L. Shaw, Joonhee Choi, Gil Refael, Manuel Endres, Soonwon Choi
Format: Article
Language:English
Published: American Physical Society 2024-11-01
Series:Physical Review X
Online Access:http://doi.org/10.1103/PhysRevX.14.041051
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author Daniel K. Mark
Federica Surace
Andreas Elben
Adam L. Shaw
Joonhee Choi
Gil Refael
Manuel Endres
Soonwon Choi
author_facet Daniel K. Mark
Federica Surace
Andreas Elben
Adam L. Shaw
Joonhee Choi
Gil Refael
Manuel Endres
Soonwon Choi
author_sort Daniel K. Mark
collection DOAJ
description We report universal statistical properties displayed by ensembles of pure states that naturally emerge in quantum many-body systems. Specifically, two classes of state ensembles are considered: those formed by (i) the temporal trajectory of a quantum state under unitary evolution or (ii) the quantum states of small subsystems obtained by partial, local projective measurements performed on their complements. These cases, respectively, exemplify the phenomena of “Hilbert-space ergodicity” and “deep thermalization.” In both cases, the resultant ensembles are defined by a simple principle: The distributions of pure states have maximum entropy, subject to constraints such as energy conservation, and effective constraints imposed by thermalization. We present and numerically verify quantifiable signatures of this principle by deriving explicit formulas for all statistical moments of the ensembles, proving the necessary and sufficient conditions for such universality under widely accepted assumptions, and describing their measurable consequences in experiments. We further discuss information-theoretic implications of the universality: Our ensembles have maximal information content while being maximally difficult to interrogate, establishing that generic quantum state ensembles that occur in nature hide (scramble) information as strongly as possible. Our results generalize the notions of Hilbert-space ergodicity to time-independent Hamiltonian dynamics and deep thermalization from infinite to finite effective temperature. Our work presents new perspectives to characterize and understand universal behaviors of quantum dynamics using statistical and information-theoretic tools.
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spelling doaj-art-f249257f712c405189d41a56c97be8712025-08-20T02:23:35ZengAmerican Physical SocietyPhysical Review X2160-33082024-11-0114404105110.1103/PhysRevX.14.041051Maximum Entropy Principle in Deep Thermalization and in Hilbert-Space ErgodicityDaniel K. MarkFederica SuraceAndreas ElbenAdam L. ShawJoonhee ChoiGil RefaelManuel EndresSoonwon ChoiWe report universal statistical properties displayed by ensembles of pure states that naturally emerge in quantum many-body systems. Specifically, two classes of state ensembles are considered: those formed by (i) the temporal trajectory of a quantum state under unitary evolution or (ii) the quantum states of small subsystems obtained by partial, local projective measurements performed on their complements. These cases, respectively, exemplify the phenomena of “Hilbert-space ergodicity” and “deep thermalization.” In both cases, the resultant ensembles are defined by a simple principle: The distributions of pure states have maximum entropy, subject to constraints such as energy conservation, and effective constraints imposed by thermalization. We present and numerically verify quantifiable signatures of this principle by deriving explicit formulas for all statistical moments of the ensembles, proving the necessary and sufficient conditions for such universality under widely accepted assumptions, and describing their measurable consequences in experiments. We further discuss information-theoretic implications of the universality: Our ensembles have maximal information content while being maximally difficult to interrogate, establishing that generic quantum state ensembles that occur in nature hide (scramble) information as strongly as possible. Our results generalize the notions of Hilbert-space ergodicity to time-independent Hamiltonian dynamics and deep thermalization from infinite to finite effective temperature. Our work presents new perspectives to characterize and understand universal behaviors of quantum dynamics using statistical and information-theoretic tools.http://doi.org/10.1103/PhysRevX.14.041051
spellingShingle Daniel K. Mark
Federica Surace
Andreas Elben
Adam L. Shaw
Joonhee Choi
Gil Refael
Manuel Endres
Soonwon Choi
Maximum Entropy Principle in Deep Thermalization and in Hilbert-Space Ergodicity
Physical Review X
title Maximum Entropy Principle in Deep Thermalization and in Hilbert-Space Ergodicity
title_full Maximum Entropy Principle in Deep Thermalization and in Hilbert-Space Ergodicity
title_fullStr Maximum Entropy Principle in Deep Thermalization and in Hilbert-Space Ergodicity
title_full_unstemmed Maximum Entropy Principle in Deep Thermalization and in Hilbert-Space Ergodicity
title_short Maximum Entropy Principle in Deep Thermalization and in Hilbert-Space Ergodicity
title_sort maximum entropy principle in deep thermalization and in hilbert space ergodicity
url http://doi.org/10.1103/PhysRevX.14.041051
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