Quantum Modeling of Device Variability in Josephson Junctions

In this talk, we present a quantum modelling framework to perform variability studies of Josephson junctions. Because quantum tunnelling depends exponentially on barrier properties, atomic-scale details – such as interface roughness and atomic contaminants – can strongly influence the performance of Josephson junctions. Our model incorporates atomic information into both the nonequilibrium Green's function (NEGF) formalism and the Bogoliubov–de Gennes (BdG) equation to simulate device variability arising from microscopic imperfections. The advantage of NEGF is associated to its analytical properties in the complex plane, which allow us to deform the contour to lower the computational cost. The BdG equation, on the other hand, provides a clear physical picture of the tunnelling process mediated by Andreev bound states. Using this approach, we analyse how interface roughness and atomic contaminants affect the Josephson energy and, ultimately, the fidelity of quantum gates.