Thermalization in a closed quantum system from randomized dynamics
- URL: http://arxiv.org/abs/2601.00056v1
- Date: Wed, 31 Dec 2025 19:00:00 GMT
- Title: Thermalization in a closed quantum system from randomized dynamics
- Authors: Nikolay V. Gnezdilov, Andrei I. Pavlov,
- Abstract summary: We show that thermal observables for a whole closed quantum system can arise in the absence of a bath.<n>We derive spin-spin correlation functions for a finite spin chain and show that they exhibit a temperature-dependent finite correlation length.<n>An implementation of this thermalization approach on a quantum computer can be utilized for thermal state preparation.
- Score: 0.0
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: The emergence of statistical mechanics from quantum dynamics is a central problem in quantum many-body physics. Deriving observables aligned with the prediction of the canonical ensemble for a quantum system relies on the presence of a bath provided either as an external environment or as a larger part of a closed system. We demonstrate that thermal (canonical) observables for a whole closed quantum system of finite size can arise in the absence of a bath. These thermal observables stem from classical averaging over randomized unitary evolutions for a few-body system. The temperature in the canonical ensemble appears as a global constraint on the total energy of the system, determined by the choice of the initial state. From averaging randomized evolutions, we derive spin-spin correlation functions for a finite spin chain and show that they exhibit a temperature-dependent finite correlation length, in agreement with the prediction of the canonical ensemble. This establishes a method for computing thermal observables in a closed, finite-size system from real-time propagation without a bath. An implementation of this thermalization approach on a quantum computer can be utilized for thermal state preparation.
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