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.
Probing excited-state dynamics of transmon ionization
3 Pith papers cite this work. Polarity classification is still indexing.
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abstract
The fidelity and quantum nondemolition character of the dispersive readout in circuit QED are limited by unwanted transitions to highly excited states at specific photon numbers in the readout resonator. This observation can be explained by multiphoton resonances between computational states and highly excited states in strongly driven nonlinear systems, analogous to multiphoton ionization in atoms and molecules. In this work, we utilize the multilevel nature of high-$E_J/E_C$ transmons to probe the excited-state dynamics induced by strong drives during readout. With up to 10 resolvable states, we quantify the critical photon number of ionization, the resulting state after ionization, and the fraction of the population transferred to highly excited states. Moreover, using pulse-shaping to control the photon number in the readout resonator in the high-power regime, we tune the adiabaticity of the transition and verify that transmon ionization is a Landau-Zener-type transition. We further extend these methods to a typical transmon with $E_J/E_C \approx 55$ and probe the offset-charge dependence of ionization dynamics in a timed-resolved manner. Our experimental results agree well with the theoretical prediction from a semiclassical driven transmon model and may guide future exploration of strongly driven nonlinear oscillators.
fields
quant-ph 3years
2026 3verdicts
UNVERDICTED 3representative 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.
Lighter fluxonium qubits show lower susceptibility to measurement-induced state transitions than heavier counterparts due to reduced multi-photon resonance density, smaller required coupling, and more harmonic charge operator structure.
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.
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Measurement-induced state transitions across the fluxonium qubit landscape
Lighter fluxonium qubits show lower susceptibility to measurement-induced state transitions than heavier counterparts due to reduced multi-photon resonance density, smaller required coupling, and more harmonic charge operator structure.