Characterization of adverse drive-induced transitions in superconducting circuits (part 2/2)

Readout and gate operations in qubits implemented in quantum superconducting circuits are performed by applying microwave drive tones to the circuit. The simultaneous pursuit of fidelity and speed of these operations by increasing drive strength is limited by unwanted drive-induced state transitions allowed by the nonlinearity.

We experimentally address the origin of these adverse state transitions in a driven transmon by measuring transition probabilities as a function of drive frequency and power. We show that there are three distinct mechanisms for adverse transitions caused by the drive: 1) excitation of intrinsic resonances between computational and non-computational states within the transmon spectrum, 2) drive-activated nonlinear processes involving extrinsic degrees of freedoms such as packaging or transmission line modes, 3) AC Stark shift of qubit frequency into resonance with lossy degrees of freedom in the qubit environment. Our findings provide insights for the improvement of readout and gate operations on superconducting qubits.

In part 2/2, we diagnose adverse drive-induced transitions in a 2D transmon in the regime when the drive frequency vastly exceeds that of the transmon.