Experimental mapping of measurement-induced state transitions in a fluxonium qubit validates numerical models predicting eleven high-error flux regions, including effects from superinductor array modes.
Measurement-induced state transitions across the fluxonium qubit landscape
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abstract
Understanding the mechanisms that limit high-fidelity readout in circuit quantum electrodynamics is essential for its optimization. Multi-photon resonances are understood to be a limiting factor, causing population transfer from the computational states to higher-energy states under drive. This effect, known as measurement-induced state transitions, has been extensively studied for the transmon qubit. While this exploration has begun for the fluxonium qubit, a systematic study of this effect is lacking. Here, we bridge this gap by theoretically studying measurement-induced state transitions in the fluxonium qubit over a wide range of parameters, comprising essentially all experimentally explored ranges. We find that lighter fluxoniums are less susceptible to these state transitions when compared to their heavier counterparts. We attribute this effect to the combination of lower density of multi-photon resonances, a smaller requisite coupling for a given dispersive shift, and a more harmonic-like structure of the charge operator. We confirm the validity of our analysis by performing time-dependent readout simulations. Finally, we consider the impact of the superinductor's array modes on measurement-induced state transitions over a large range of parameters.
fields
quant-ph 2years
2026 2verdicts
UNVERDICTED 2representative citing papers
In two-transmon systems, a spectator qubit lowers the MIST threshold of the readout qubit and can itself be affected by the readout qubit's transitions, with a coupler further modifying both effects.
citing papers explorer
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Experimental Characterization and Modeling of Measurement-Induced State-Transitions in a Fluxonium Superconducting Qubit
Experimental mapping of measurement-induced state transitions in a fluxonium qubit validates numerical models predicting eleven high-error flux regions, including effects from superinductor array modes.
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Measurement-induced state transitions in multi-qubit transmon processors
In two-transmon systems, a spectator qubit lowers the MIST threshold of the readout qubit and can itself be affected by the readout qubit's transitions, with a coupler further modifying both effects.