SciPost Physics

SciPost Phys. 9, 004 (2020) · published 8 July 2020

• doi: 10.21468/SciPostPhys.9.1.004
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Abstract

We study the equilibration properties of isolated ergodic quantum systems initially prepared in a cat state, i.e a macroscopic quantum superposition of states. Our main result consists in showing that, even though decoherence is at work in the mean, there exists a remnant of the initial quantum coherences visible in the strength of the fluctuations of the steady state. We back-up our analysis with numerical results obtained on the XXX spin chain with a random field along the z-axis in the ergodic regime and find good qualitative and quantitative agreement with the theory. We also present and discuss a framework where equilibrium quantities can be computed from general statistical ensembles without relying on microscopic details about the initial state, akin to the eigenstate thermalization hypothesis.

• Pappalardi et al., Eigenstate Thermalization Hypothesis and Free Probability
  Phys. Rev. Lett. 129, 170603 (2022) [Crossref]
• Hruza et al., Coherent Fluctuations in Noisy Mesoscopic Systems, the Open Quantum SSEP, and Free Probability
  Phys. Rev. X 13, 011045 (2023) [Crossref]