Measurement-Induced State Transitions in a Superconducting Qubit: Within the Rotating Wave Approximation

Understand

Superconducting qubits typically use a dispersive readout scheme, where a resonator is coupled to a qubit such that its frequency is qubit-state dependent.

• Measurement is performed by driving the resonator, where the transmitted resonator field yields information about the resonator frequency and thus the qubit state.
• Ideally, we could use arbitrarily strong resonator drives to achieve a target signal-to-noise ratio in the shortest possible time.
• However, experiments have shown that when the average resonator photon number exceeds a certain threshold, the qubit is excited out of its computational subspace in a process we refer to as a measurement-induced state transition (MIST).