Investigations of 1/f Magnetic Flux Noise in Superconducting Qubits with Weak Magnetic Fields*

Low-frequency 1/f magnetic flux noise is known to limit the coherence of superconducting qubits, yet an understanding of its microscopic origins is still lacking. Although magnetically coupled surface defects, so-called “surface spins,” are widely accepted to be the source, their identities and interaction mechanisms remain an open question. We showed in recent experiments on aluminum C-shunt flux qubits [1] that the noise power spectrum responds anomalously to the application of weak in-plane magnetic fields. We report on the continuation of these studies, particularly focusing on advanced noise spectroscopy techniques and field-orientation dependence.

[1] D. A. Rower et al., Phys. Rev. Lett. 130, 220602 (2023).