Charge-Tuned Measurement-Induced State Transitions in a Transmon Qubit

High-fidelity, rapid readout of superconducting qubits is essential for scalable quantum computing. Yet an inappropriate readout drive or non-ideal qubit design often undermines the non-demolition character of measurement through unwanted level transitions. In this work, we investigate measurement-induced state transitions (MIST) in a charge-sensitive transmon qubit, focusing on how the gate-charge offset and resonator photon number jointly govern the probability High-fidelity, rapid readout of superconducting qubits is essential for scalable quantum computing. Yet an inappropriate readout drive or non-ideal qubit design often undermines the non-demolition character of measurement through unwanted level transitions. In this work, we investigate measurement-induced state transitions (MIST) in a charge-sensitive transmon qubit, focusing on how the gate-charge offset and resonator photon number jointly govern the probability of leakage out of the computational subspace during dispersive readout. Building on the recent high-frequency readout model free from multi-excitation resonances, we vary both and and measure post-readout populations in higher excited states. We observe a non-monotonic dependence of the transition probability on and find that the “hot-spots” of leakage shift as a function of the . Importantly, these results validate the underlying model and provide a good prediction for safer readout regimes, revealing a clear inform the design rule for transmon qubits. These findings broaden the practical readout-design paradigm and provide actionable guidance for maintaining QND fidelity in transmon-based quantum processors.

n of the . Importantly, these results validate the underlying model and provide a good prediction for safer readout regimes, revealing a clear inform the design rule for transmon qubits. These findings broaden the practical readout-design paradigm and provide actionable guidance for maintaining QND fidelity in transmon-based quantum processors.