Statistical Mechanics of Random Mixed State Ensembles with Fixed Energy

Fuente: arXiv
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Autor principal: Miller, Harry J. D.
Formato: Preprint
Publicado: 2025
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author Miller, Harry J. D.
author_facet Miller, Harry J. D.
contents Mixed state ensembles such as the Bures-Hall and Hilbert-Schmidt measure are probability distributions that characterise the statistical properties of random density matrices and can be used to determine the typical features of mixed quantum states. Here we extend this framework by considering the properties of random states with fixed average energy, and the ensemble-averaged density matrix is derived under this additional physical constraint. This gives rise to a type of microcanonical ensemble for random mixed states and we connect its properties to a statistical mechanical entropy and temperature. Our results are illustrated using a variety of simple spin systems, and we find that they can exhibit exotic features such as phase transitions in the absence of energetic interactions and finite relative energy fluctuations in the thermodynamic limit.
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publishDate 2025
record_format arxiv
spellingShingle Statistical Mechanics of Random Mixed State Ensembles with Fixed Energy
Miller, Harry J. D.
Quantum Physics
Mixed state ensembles such as the Bures-Hall and Hilbert-Schmidt measure are probability distributions that characterise the statistical properties of random density matrices and can be used to determine the typical features of mixed quantum states. Here we extend this framework by considering the properties of random states with fixed average energy, and the ensemble-averaged density matrix is derived under this additional physical constraint. This gives rise to a type of microcanonical ensemble for random mixed states and we connect its properties to a statistical mechanical entropy and temperature. Our results are illustrated using a variety of simple spin systems, and we find that they can exhibit exotic features such as phase transitions in the absence of energetic interactions and finite relative energy fluctuations in the thermodynamic limit.
title Statistical Mechanics of Random Mixed State Ensembles with Fixed Energy
topic Quantum Physics
url https://arxiv.org/abs/2508.00809