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It has previously been suggested that small subsystems of closed quantum systems thermalize under some assumptions; however, this has been rigorously shown so far only for systems with very weak interaction between subsystems. In this work,…

Quantum Physics · Physics 2021-03-31 Markus P. Mueller , Emily Adlam , Lluis Masanes , Nathan Wiebe

We show, without relying on any unproven assumptions, that a low-density free fermion chain exhibits thermalization in the following (restricted) sense. We choose the initial state as a pure state drawn randomly from the Hilbert space in…

Statistical Mechanics · Physics 2026-04-13 Naoto Shiraishi , Hal Tasaki

Typicality arguments replace the postulated mixed state ensembles of statistical mechanics with pure states sampled uniformly at random, explaining why most microstates of large systems exhibit thermal behavior. This paradigm has been…

Quantum Physics · Physics 2025-05-01 Pedro S. Correia , Gabriel Dias Carvalho , Thiago R. de Oliveira

We study the emergence over time of a universal, uniform distribution of quantum states supported on a finite subsystem, induced by projectively measuring the rest of the system. Dubbed deep thermalization, this phenomenon represents a form…

Quantum Physics · Physics 2023-01-04 Matteo Ippoliti , Wen Wei Ho

Thermalization of an isolated quantum system has been a nontrivial problem since the early days of quantum mechanics. In generic isolated quantum systems, nonequilibrium dynamics is expected to result in thermalization, indicating the…

Quantum Physics · Physics 2024-04-22 Tanmay Saha , Pratik Ghosal , Pratapaditya Bej , Abhishek Banerjee , Prasenjit Deb

If we prepare an isolated, interacting quantum system in an eigenstate and perturb a local observable at an initial time, its expectation value will relax towards a thermal expectation value, even though the time evolution of the system is…

Quantum Physics · Physics 2024-06-04 Tobias Helbig , Tobias Hofmann , Ronny Thomale , Martin Greiter

We consider conditions under which an isolated quantum system approaches a microcanonical equilibrium state. A key component is the eigenstate thermalisation hypothesis, which proposes that all energy eigenstates appear thermal. We…

Quantum Physics · Physics 2021-09-01 Joe Dunlop , Oliver Cohen , Anthony J. Short

Understanding the rich spatial and temporal structures in nonequilibrium thermal environments is a major subject of statistical mechanics. Because universal laws, based on an ensemble of systems, are mute on an individual system, exploring…

Statistical Mechanics · Physics 2019-04-19 Liyi Zhao , Ping Fang , Chushun Tian

"Deep thermalization" describes the emergence of universal wavefunction distributions in quantum many-body dynamics, appearing on a local subsystem upon measurement of its environment. In this work, we study in detail the effect of…

Quantum Physics · Physics 2025-06-11 Rui-An Chang , Harshank Shrotriya , Wen Wei Ho , Matteo Ippoliti

We investigate the equilibration and thermalization properties of quantum systems interacting with a finite dimensional environment. By exploiting the concept of time averaged states, we introduce a completely positive map which allows to…

Quantum Physics · Physics 2012-11-27 A. Smirne , E. -M. Laine , H. -P. Breuer , J. Piilo , B. Vacchini

Recently, there have been significant new insights concerning conditions under which closed systems equilibrate locally. The question if subsystems thermalize---if the equilibrium state is independent of the initial state---is however much…

Quantum Physics · Physics 2012-10-02 M. Cramer

We discuss how the thermalization of an elementary quantum system is modified when the system is placed in an environment out of thermal equilibrium. To this aim we provide a detailed investigation of the dynamics of an atomic system placed…

Quantum Physics · Physics 2013-01-16 Bruno Bellomo , Riccardo Messina , Didier Felbacq , Mauro Antezza

This paper is concerned with the ergodic subspaces of the state spaces of isolated quantum systems. We prove a new ergodic theorem for closed quantum systems which shows that the equilibrium state of the system takes the form of a grand…

Quantum Physics · Physics 2008-11-26 Dorje C. Brody , Daniel W. Hook , Lane P. Hughston

We consider the dynamics of an arbitrary quantum system coupled to a large arbitrary and fully quantum mechanical environment through a random interaction. We establish analytically and check numerically the typicality of this dynamics, in…

Quantum Physics · Physics 2017-07-26 Grégoire Ithier , Florent Benaych-Georges

A single mechanism, endemic to the standard model of physics, is proposed to explain wavefunction collapse, classical motion, dissipation, equilibration, and the transition from pure quantum mechanics through open system decoherence to the…

General Physics · Physics 2024-09-23 J. H. Brownell

Simulations are performed of a small quantum system interacting with a quantum environment. The system consists of various initial states of two harmonic oscillators coupled to give normal modes. The environment is "designed" by its level…

Statistical Mechanics · Physics 2015-06-15 George L. Barnes , Michael E. Kellman

The thermodynamics of quantum systems driven out of equilibrium has attracted increasing attention in last the decade, in connection with quantum information and statistical physics, and with a focus on non-classical signatures. While a…

Quantum Physics · Physics 2022-06-01 Gonzalo Manzano , Roberta Zambrini

The theory of quantum thermodynamics investigates how the concepts of heat, work, and temperature can be carried over to the quantum realm, where fluctuations and randomness are fundamentally unavoidable. These lecture notes provide an…

Quantum Physics · Physics 2026-04-17 Patrick P. Potts

We uncover emergent universality arising in the equilibration dynamics of multimode continuous-variable systems. Specifically, we study the ensemble of pure states supported on a small subsystem of a few modes, generated by Gaussian…

Quantum Physics · Physics 2024-12-25 Chang Liu , Qi Camm Huang , Wen Wei Ho

The deterministic and time-reversal symmetric dynamics of isolated quantum systems is at odds with irreversible equilibration observed in generic thermodynamic systems. Standard approaches at a reconciliation employ subjective restrictions…

Quantum Physics · Physics 2025-11-07 Aritro Mukherjee