Understanding Multiscale Disorder in Superconducting Nanowire Single‐Photon Detectors1

Superconducting nanowire single‐photon detectors are central to applications across quantum information science, but their performance is constrained by the effects of disorder and electrodynamic inhomogeneities that are not well understood. By combining DC transport, dark‐count measurements, and bias‐dependent microwave transmission spectroscopy in the presence of controlled nanoscale disorder introduced through helium–ion irradiation, local instabilities and global superfluid response are distinguished. This approach enables controlled tuning of the depairing current, kinetic inductance, microwave dissipation, and mode structure within a single device through systematic variation of the ion fluence. Bias‐ and temperature‐dependent resonance shifts quantify disorder‐induced modifications of the superconducting density of states through the nonlinear kinetic inductance, while the emergence of multiple resonant modes reveals the formation of electrodynamically distinct superconducting regions. The combined microwave response, characterized by the resonance frequency and quality factor , provides qualitative fingerprints of perturbation‐dependent microwave dissipation under bias current, temperature, perpendicular magnetic field, RF power, and disorder, thereby establishing a multifunctional foundation for disorder engineering of superconducting nanowire detectors and resonators.