Ti and Al-Ti thin films for quasiparticle trapping in superconducting quantum circuits

Abstract

Quasiparticles are unwanted excitations of Cooper pairs that disrupt superconductivity and undermine the performance of superconducting qubits. To mitigate this effect, engineered regions of lower superconducting gap energy that capture broken Cooper pairs, known as quasiparticle traps, can be implemented. In this work, as a first step towards the realization of a quasiparticle trapping experiment on the shunting capacitor plates of a 2D transmon-type qubit, a recipe for the deposition of titanium and aluminium-titanium thin films of different thicknesses has been developed and successfully implemented. The room-temperature conductance characteristics of the films have been assessed, and their dependence on film thickness has been ascertained.