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Equilibrium fluctuations in maximally noisy extended quantum systems

Abstract : We introduce and study a class of models of free fermions hopping between neighbouring sites with random Brownian amplitudes. These simple models describe stochastic, diffusive, quantum, unitary dynamics. We focus on periodic boundary conditions and derive the complete stationary distribution of the system. It is proven that the generating function of the latter is provided by the Harish-Chandra-Itzykson-Zuber integral which allows us to access all fluctuations of the system state. The steady state is characterized by non trivial correlations which have a topological nature. Diagrammatic tools appropriate for the study of these correlations are presented. In the thermodynamic large system size limit, the system approaches a non random equilibrium state plus occupancy and coherence fluctuations of magnitude scaling proportionally with the inverse of the square root of the volume. The large deviation function for those fluctuations is determined. Although decoherence is effective on the mean steady state, we observe that sub-leading fluctuating coherences are dynamically produced from the inhomogeneities of the initial occupancy profile.
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Contributor : Anne-Cécile Verzier <>
Submitted on : Thursday, November 12, 2020 - 3:21:53 PM
Last modification on : Tuesday, December 8, 2020 - 3:33:31 AM
Long-term archiving on: : Saturday, February 13, 2021 - 7:48:33 PM


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Michel Bauer, Denis Bernard, Tony Jin. Equilibrium fluctuations in maximally noisy extended quantum systems. SciPost Physics, SciPost Foundation, 2019, 6 (4), pp.045. ⟨10.21468/SciPostPhys.6.4.045⟩. ⟨hal-02367770⟩



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