Toward multiscale simulations for technology computer-aided design of superconducting qubits*

Technology computer-aided design (TCAD) software is an important device engineering tool enabling to simulate and optimize component behavior before lengthy and costly manufacturing steps. While commercial TCAD software has been used for semiconductor chip design for decades, usage of TCAD in the superconducting qubit community is more recent, and largely based on conventional microwave engineering tools.

Going beyond established microwave engineering paradigms in predictive superconducting qubit TCAD is challenging due to the necessity to calculate parameters that are determined at vastly different length scales. While capacitances and inductances may be efficiently determined from standard finite-element simulation tools, properties of Josephson junctions are often determined by physics at the atomic scale.

We will present transmon simulations using an adaptive meshing algorithm enabling accurate capacitance extraction despite challenges posed by singularities such as corners and embedded surfaces, which are typical of superconducting-qubit structures. We will then present ab initio simulations of Josephson junctions using the Non-equlibrium Green’s Function Density Functional Theory (NEGF-DFT) technique. Together, these results pave the way to a fully integrated multiscale simulation software suite for superconducting qubit design.