Flat-band Localization and Interaction-Induced Delocalization of Photons

08/11/2023, 2:45pm-3:00pm

Lattices with dispersionless, or flat, energy bands have attracted significant interest in part due to the strong dependence of particle dynamics on interactions. Using superconducting transmon qubits, we design a plaquette of a lattice whose band structure consists entirely of flatbands under the addition of a synthetic magnetic field of pi. We first observe compact localization in the dynamics of a single particle, the hallmark of all-bands-flat physics. Next, we initialize two photons bound by interactions on the same site and observe an interaction-enabled delocalized walk across the plaquette. These results mark the first experimental observation of a quantum walk that becomes delocalized due to interactions and establish superconducting circuits as a platform for studies of flat-band-lattice dynamics with strong interactions.