Magneto-Electric Coupling of Noise and Loss-Generating Paramagnetic Spins in Superconducting Circuits

Noise and loss in superconducting circuits caused by fluctuating charge and magnetic flux represent significant challenges for the realization of large-scale quantum computing architectures. Previous experimental [Phys. Rev. Applied 6 041001 (2016), Phys. Rev. Lett. 118, 057703 (2017)] and theoretical [PRL 112 017001 (2014)] work has identified O2, OH, and atomic H surface adsorbates as possible sources of flux noise in superconducting circuits. We report here on an extension to our model for the flux noise generated by the dynamics of an ensemble of paramagnetic spins on adsorbed O2 molecules to include electric charge density differences associated with spin flips. This model combines a thermodynamic ensemble generated with Monte Carlo simulations with Landau-Lifshitz-Gilbert equation simulations for the dynamics and is parametrized with vdW-corrected density functional theory calculations. From this model we evaluate the effects of external electric and magnetic fields on the phases of the spin system, its dynamics, and the charge and flux noise generated.