Science · 2019 · 519 citations · 55 references
Disordered interacting quantum systems can fail to thermalize, breaking thermodynamics, and understanding this requires measuring entanglement, which is experimentally challenging. The study aims to realize a many‑body‑localized system in a disordered Bose‑Hubbard chain and characterize its entanglement properties. This is achieved by measuring particle fluctuations and correlations in the chain. The experiment shows particle localization suppresses transport and prevents subsystem thermalization, reveals non‑local correlations that grow logarithmically—signifying entanglement entropy growth—and demonstrates that many‑body localization is qualitatively distinct from non‑interacting disorder localization.
An interacting quantum system that is subject to disorder may cease to thermalize due to localization of its constituents, thereby marking the breakdown of thermodynamics. The key to our understanding of this phenomenon lies in the system's entanglement, which is experimentally challenging to measure. We realize such a many-body-localized system in a disordered Bose-Hubbard chain and characterize its entanglement properties through particle fluctuations and correlations. We observe that the particles become localized, suppressing transport and preventing the thermalization of subsystems. Notably, we measure the development of non-local correlations, whose evolution is consistent with a logarithmic growth of entanglement entropy - the hallmark of many-body localization. Our work experimentally establishes many-body localization as a qualitatively distinct phenomenon from localization in non-interacting, disordered systems.
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Quantum statistical mechanics in a closed system
J. M. Deutsch · Physical Review A · 1991 · 2.8K citations