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2. October 2018 10:00

Quantum criticality and reversible information scrambling

Dr. Quirin Hummel
Theoretische Physik, Universität Regensburg

We consider a quantum critical one-dimensional model of bosons with attractive interactions that displays a generic critical separatrix structure in the phase space governing the mean field dynamics. A semiclassical quantization of the latter, where a large but finite number of particles plays the role of a small quantum of action, allows us to account for many-body correlations crucial to the behavior at criticality. In particular, it enables analytical quantification of the spectral gap and a logarithmic scaling of local level spacings. The latter become asymptotically constant, resembling harmonicity, while associated with a unique Ehrenfest-like time scale that mimicks chaos. This interplay results in the counterintuitive coexistence of initial fast information scrambling and asymptotically perfect memory, observed as quasiperiodic revivals, e.g. present in the one-body entropy. By identifying the emergence of local Ehrenfest-like time scales during separatrix quantization as the generic decicive mechanism this constitutes a hallmark of criticality in integrable many-body systems.