Measuring charge and flux noise correlations with a superconducting qubit

Superconducting qubits are a promising approach towards scalable quantum computing. Coherence times in state-of-the-art devices are now in excess of 100 us. While these times are impressive, achieving the necessary fidelities for suitably scalable surface code algorithms requires better coherence times, and as such, a better understanding of the microscopic origin of the fluctuators that gives rise to different noise sources (e.g., flux noise, charge noise, and dielectric noise).
Recent evidence suggests that significant contribution to charge and flux noise arise from surface defects. Thus, a natural question to further understand the specific mechanism of the noise is if charge and flux noise originate from the same set of surface defects. To this end, we have designed and fabricated a charge-sensitive transmon device. Here we discuss the results of Ramsey-based power spectral density measurements on charge-parity noise (due to quasiparticle tunneling), charge noise, as well as a Ramsey-based cross power spectral density measurement between charge and flux noise. These results indicate valid microscopic models of the fluctuators that give rise to charge and flux noise.