Dielectric loss in long arrays of Josephson junctions

Understanding and mitigating loss mechanisms is critical for enhancing the performance of superconducting qubits. Our work explores a novel approach to investigating dielectric loss in Al/AlOx/Al Josephson junctions over a wide frequency range. We utilize a multi-mode Fabry-Pérot cavity made of two parallel arrays of up to twenty thousand junctions. By exploiting the weak cross-Kerr interaction between the cavity’s standing wave modes, we perform a two-tone time-domain experiment and extract the lifetime of the modes, spanning from a few tens of MHz to ten GHz. Our approach allows for the characterization of dielectric loss across thousands of junctions and over eight octaves in frequencies, offering new insights into its behavior.