High Impedance Granular Aluminum Ring Resonators

Superconducting inductors with impedance surpassing the resistance quantum, i.e., superinductors, are important for quantum technologies because they enable the development of 

protected qubits, enhance coupling to systems with small electric dipole moments, and facilitate the study of phase-slip physics. We demonstrate superinductors with densely packed 

meandered traces of granular aluminum (grAl) with inductances up to , achieving impedances exceeding  in the  range. Ring resonators made with grAl 

meandered superinductors exhibit quality factors on the order of  in the single-photon regime and low non-linearity on the order of tens of . Depending on the grAl resistivity, 

at , we measure frequency noise spectral densities in the range of  to . In some devices, in the single-photon regime, we observe a positive Kerr coefficient of 

unknown origin. Using more complex fabrication, the devices could be released from the substrate, either freestanding or suspended on a membrane, thereby further improving their 

impedance by a factor of three.