Measurement-induced state transitions in multi-qubit transmon processors

• URL: http://arxiv.org/abs/2606.05010v1
• Date: Wed, 03 Jun 2026 15:30:38 GMT
• Title: Measurement-induced state transitions in multi-qubit transmon processors
• Abstract summary: Dispersive readout of the transmon qubit in circuit QED is known to lose its quantum non-demolition character at small measurement drive amplitudes.<n>We show that the presence of other components, such as qubits and couplers, can affect the MIST threshold of a measured transmon.
• Score: 70.39941373070748
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Dispersive readout of the transmon qubit in circuit QED is known to lose its quantum non-demolition character at small to moderate measurement drive amplitudes. This phenomenon is understood to originate from Laundau-Zener transitions at accidental multi-photon resonances, where $n$ drive photons can promote the transmon by $m$ levels. This interpretation has been shown to be in agreement with experiments characterizing the dispersive readout of a single transmon. The impact of these measurement-induced state transition (MIST) of a transmon embedded in a multi-qubit chip, however, remains largely unexplored. Here, we show that the presence of other components, such as qubits and couplers, can affect the MIST threshold of a measured transmon. To arrive at these results, we present a general method to characterize measurement-induced transition when the qubit under readout is coupled to other circuit elements, a ubiquitous situation in circuit QED-based quantum processors. As an example, we consider the case of two transmon qubits, and we show that the spectator qubit can be impacted by the measurement-induced transition of the readout qubit and, conversely, that the presence of the spectator qubit can lower the MIST threshold of the readout qubit. Finally, we explore how adding a coupler mode between the two qubits further modifies these effects.

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