Driven-Dissipative Interpretation of Measurement-Induced State Transitions Beyond Semiclassical Predictions

TL;DR

This paper offers a quantum-driven model to understand measurement-induced state transitions in superconducting qubits, revealing new regimes like super-MIST and transient states that impact measurement fidelity.

Contribution

It introduces a driven-dissipative quantum model that captures dynamics beyond semiclassical predictions, uncovering super-MIST and transient regimes in qubit readout.

Findings

Identification of super-MIST with steady-state qubit inversion

Discovery of transient readout conditions with high resonator population

Demonstration of dynamics beyond semiclassical Landau-Zener predictions

Abstract

Dispersive readout plays a central role in superconducting quantum computing, enabling quantum nondemolition (QND) measurements of qubits through a coupled microwave resonator. However, under strong readout drives, multi-photon resonances can cause measurement-induced state transition (MIST), resulting in qubit leakage out of the computational subspace and compromising the QND character. We present a driven-dissipative interpretation of MIST using a reduced quantum model that captures the dynamics and entanglement structure underlying the breakdown of QND measurement, a feature inaccessible to previous semiclassical treatments. A super-MIST regime under strong drive is uncovered, characterized by steady-state qubit inversion and slow relaxation beyond the semiclassical Landau-Zener predictions. We further identify a transient readout condition in which the resonator becomes highly populated while the qubit remains near its original state. These results are broadly applicable to superconducting qubits such as fluxonium and transmon, unveil the nonequilibrium dynamics of MIST, and highlight strongly driven regimes that can be leveraged for measurement optimization.