Thermalization in a closed quantum system from randomized dynamics
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866911349918924800 |
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| author | Gnezdilov, Nikolay V. Pavlov, Andrei I. |
| author_facet | Gnezdilov, Nikolay V. Pavlov, Andrei I. |
| contents | 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_00056 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Thermalization in a closed quantum system from randomized dynamics Gnezdilov, Nikolay V. Pavlov, Andrei I. Statistical Mechanics Quantum Physics 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. |
| title | Thermalization in a closed quantum system from randomized dynamics |
| topic | Statistical Mechanics Quantum Physics |
| url | https://arxiv.org/abs/2601.00056 |