Measurement catastrophe and ballistic spread of charge density with vanishing current

Abstract

One of the features of many-body quantum systems with Hilbert-space fragmentation are stationary states manifesting quantum jamming. It was recently shown that these are "states with memory", in which, e.g., measuring a localised observable has everlasting macroscopic effects. We study such a measurement catastrophe with an example that stands out for its clarity. We show in particular that at late times the expectation value of a charge density becomes a nontrivial function of the ratio between distance and time notwithstanding the corresponding current approaching zero.

Nonequilibrium symmetry-protected topological order: Emergence of semilocal Gibbs ensembles

“…-Macroscopic effects triggered by a local perturbation had been observed before in the case of symmetry-breaking perturbations of ground states [138,139], and excited states in a jammed sector [62,140]. Whether they are just a different facet of the same phenomenon as described herein, and characterized by the logarithmic scaling of the excess entropy, remains unclear.…”

Sublattice entanglement in an exactly solvable anyonlike spin ladder

“…This motivates the study of selected integrable models with even simpler dynamics, where there is some interaction in the system, nevertheless closed form results can be derived for the real time evolution of certain physical quantities. Such models include the Rule54 cellular automaton [12][13][14][15][16][17], the box-ball systems [10,18,19], classical cellular automata of the XXC type [9,[20][21][22][23][24], nontrivial strong coupling limits of known models [25][26][27] including the folded XXZ model [28][29][30][31], or quantum circuits that are both integrable and dual-unitary [32]. A common property of these models is that the scattering of the particles (either classical or quantum) is rather simple compared to a generic integrable model.…”