Abstract

Complex entanglement structures in many-body quantum systems offer potential benefits for quantum technology, yet their applicability tends to be severely limited by thermal excitations and disorder. In this talk, I will present our recent efforts to utilize a custom-built superconducting qubit ladder to realize non-thermalizing states with rich entanglement structures in the middle of the energy spectrum. Despite effectively forming an ``infinite” temperature ensemble, these states robustly encode quantum information far from equilibrium, as we demonstrate by measuring the fidelity and entanglement entropy in the quench dynamics of the ladder. Our approach harnesses the recently proposed type of non-ergodic behavior known as ``rainbow scar”, which allows us to obtain analytically exact eigenfunctions whose ergodicity-breaking properties can be conveniently controlled by randomizing the couplings of the model, without affecting their energy. The on-demand tunability of entanglement structure via disorder allows for in situ control over ergodicity breaking and it provides a knob for designing exotic many-body states that defy thermalization.