Loss estimation using Energy Participation Ratio in KQCircuits

In the last decade, superconducting circuits have become one of the most promising platforms for quantum computing. However, the current quantum circuits and algorithms in the noisy intermediate-scale quantum era would benefit from longer qubit coherence. To this end, we present a new addition to KQCircuits (KQC) [1]. Support for energy participation ratio simulations is implemented by employing an open-source toolbox named pyEPR [2]. KQC is a GPLv3-licensed layout design tool developed at IQM Finland for creating state-of-the-art superconducting circuits and processors.

With the introduction of pyEPR, users may with ease estimate qubit parameters, such as, energy levels and effects of material losses. Adding on top of existing automated simulations provided by KQC, pyEPR is­ seamlessly integrated into the workflow. A design from KQC can be exported to a pyEPR-compatible format and used in optimising the design.

In this work we study the contribution of two-level system losses in various interfaces to the quality factor of superconducting resonators and compare to measurements in order to extract scaling behaviour. We further apply the results to analyse real-world qubit geometries, demonstrating how this tool can facilitate the further development of high-coherence superconducting quantum devices.

[1] J. Heinsoo et al., ‘KQCircuits’. IQM Finland, Jun. 2021. GPLv3. doi: 10.5281/zenodo.4944796.

[2] Z. K. Minev et al., ‘pyEPR’. May. 2021. BSD. doi: 10.5281/zenodo.4744448.