Mitigation of Measurement-Induced State Transitions via a Fast-Load and Fast-Clear Readout

  1. Wei-En Lin,
  2. Li-Chieh Hsiao,
  3. Chen-Hsun Ma,
  4. Erh-Hsiang Yeh,
  5. Wei-Lun Peng,
  6. Hsi-Sheng Goan,
  7. Cen-Shawn Wu,
  8. Yueh-Nan Chen,
  9. Yung-Fu Chen,
  10. Chung-Ting Ke,
  11. and Chii-Dong Chen
High-fidelity and rapid qubit readout is essential for superconducting quantum processors, typically realized through the quantum non-demolition (QND) dispersive interaction within a qubit-resonator architecture. However, the achievable readout speed and fidelity are fundamentally limited by measurement-induced state transitions (MIST). For a transmon qubit, MIST is highly sensitive to the offset charge ng due to the charge dispersion of its higher-lying energy levels. In this work, we systematically investigate ng-dependent MIST dynamics governed by the diabaticity and symmetry of pulse shaping within a charge-sensitive transmon architecture. We engineer fast-load and fast-clear pulses that effectively suppress resonator photon overshoots, thereby demonstrating a highly practical strategy to mitigate MIST without requiring complex waveforms or real-time feedback. Utilizing active gate-voltage control and rapid feedback, the measurement-induced transition probability is precisely mapped against ng and the steady-state resonator photon number, exhibiting strong agreement with numerical Floquet branch analysis. Ultimately, we evaluate the ng-averaged total error probabilities for both readout and post-readout stages, verifying that a straightforward three-step pulse scheme consistently minimizes overall readout errors. Within the framework of large-scale superconducting quantum processors, this practical, hardware-free approach inherently offers a better trade-off between the readout signal-to-noise ratio and QND preservation.
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