Low loss lumped-element inductors made from granular aluminum - part 2

Granular Aluminum (grAl) is a promising material for building inductive shunts in superconducting quantum circuits. However, long lived quasiparticles (QPs) are suspected to limit coherences in grAl devices [1]. In addition to the loss mechanisms investigated in part 1 of this two part talk, it is also important to understand the role QPs play in limiting the coherences of such circuits. In part 2 of this talk, we investigate QP time dynamics in lumped-element all-grAl resonators and in hybrid grAl-Ta resonators, by measuring their frequency response after high energy impacts. Interestingly, for all of our lumped element resonators we infer QP relaxation times that are 1000x faster than previously reported for grAl resonators made with films of a similar normal-state resistivity. Based on a heuristic model [2], the lumped-element grAl resonators show QP time dynamics similar to that of a standard 3D transmon. Further we discuss the dependence of these dynamics on resonator geometry and film parameters.



[1] L. Grünhaupt et al., Loss Mechanisms and Quasiparticle Dynamics in Superconducting Microwave Resonators Made of Thin-Film Granular Aluminum, Physical Review Letters 121, 117001 (2018).

[2] C. Wang et al., Measurement and control of quasiparticle dynamics in a superconducting qubit, Nature Communications 5, 5836 (2014).