Quantum tomography of the superfluid-insulator transition for a mesoscopic atomtronic ring

Abstract

We provide a phase-space perspective for the analysis of the superfluid-insulator transition for finite-size Bose-Hubbard circuits. We explore how the eigenstates parametrically evolve as the inter-particle interaction is varied, paying attention to the fingerprints of chaos at the quantum phase-transition. Consequently, we demonstrate that the tomographic spectrum reflects the existence of mixed-regions of chaos and quasi-regular motion in phase-space. This tomographic semiclassical approach is much more efficient and informative compared to the traditional "level statistics" inspection. Of particular interest is the characterization of the fluctuations that are exhibited by the many-body eigenstates. In this context, we associate with each eigenstate a Higgs measure for the identification of amplitude modes of the order-parameter. Finally we focus on the formation of the lowest Goldstone and Higgs bands.