New publication on ultrastrong coupling

In this paper , Alba Torras-Coloma, Luca Cozzolino, Ariadna Gómez del Pulgar Martínez, Elia Bertoldo and Pol Forn-Díaz present an ultrastrong superinductor-based coupling mechanism in a flux qubit galvanically coupled to an LC resonator. Using granular aluminum as a high-inductance coupler, they achieve ultrastrong interaction despite the qubit’s very small persistent current. Spectroscopy reveals a coupling ratio characteristic of the perturbative ultrastrong regime.