Interacting two-level defects as sources of fluctuating high-frequency noise in superconducting circuits

Defect two-level systems (TLS) ensembles are well known to be responsible for the low-frequency noise in solid-state mesoscopic devices, but are generally considered to be non-interacting. A model based on interactions between TLS, believed to reside in the surface oxide covering the superconducting material, provides a novel mechanism to explain the noise fluctuations that are present in virtually all superconducting circuit designs, the origins of which have remained elusive so far.