The Role of Atomic Structure in Imperfect Josephson Junctions

Josephson junctions are key components of superconducting qubits, which are one of the most promising candidates to realise large-scale quantum computing. The performance of these qubits is limited by our understanding of the materials science of Josephson junctions. Imperfections in the materials of Josephson junction devices are a source of energy dissipation, decoherence, parameter drift, and uncertainty. We utilise an atomistic model of Al-AlOx-Al Josephson junctions as a method to study pinhole imperfections in the oxide tunnel barrier. With the non-equilibrium Green's function formalism we study quasiparticle transport through devices, and extend these methods to study the superconducting current-phase relationship using two different approaches. Additionally we study a recently developed alternating bias assisted annealing technique computationally to understand its effect on atomic movement within the barrier, and device parameters such as the normal resistance and critical current. This work aims to provide insights to inform and optimise the fabrication processes of Al-AlOx-Al Josephson junctions, supporting advancements in quantum computing technology.<p></p>