Mechanisms of drive-induced unwanted state transitions in superconducting circuits

Microwave drives are essential for implementing control and readout operations in superconducting quantum circuits. However, the speed and fidelity of such operations are eventually limited by the drive-induced unwanted state transitions (DUST). We classify the underlying mechanisms of these transition into three categories: (1) resonant energy exchange with parasitic two-level system (TLS), activated by ac-Stark shifts, (2) multi-photon processes intrinsic to the circuit Hamiltonian, and (3) inelastic scattering processes in which the drive excites the superconducting circuit while transferring excess energy to spurious electromagnetic modes or TLS defects. 

In this talk, we provide a comprehensive framework for experimentally characterizing and theoretically predicting DUST. By investigating a transmon driven across a 9 GHz frequency range, we identify the physical origins of all prominent transitions and summarize the signatures of each transition mechanism. Furthermore, we demonstrate that the Floquet steady-state simulation, complemented by an electromagnetic simulation of the physical device, accurately predicts the observed transitions that do not involve TLS. These results suggest a set of layered mitigation strategies through informed choices of drive frequency and improved circuit design.