Measurement-induced state transitions in a superconducting qubit: Within the rotating-wave approximation

Fast nondemolition measurement of superconducting qubits is important for the operation of quantum computers, but readout is constrained by measurement-induced state transitions that shift the qubit population outside of its computational subspace. This work experimentally characterizes the phenomenon and provides an intuitive model to explain its physical process. Surprisingly, the offset charge of the transmon qubit, which is usually ignored, is important in explaining the experiments. These results inform engineering and physics-based solutions to this problem by providing performance limits for the dispersive readout of superconducting qubits.