Speaker
Description
Qubit readout is essential and fundamental to qubit fidelity. Currently, qubit readout still suffers from thermal excitation, transition, and control errors. Although active reset could ease part of the issues, it increases the operation overhead. To mitigate these issues, we explore the effect of package and readout measurement-induced state transitions (MIST) based on our superconducting transmon qubits. We first investigate the effect of the package on cooling our superconducting qubits. We developed a three-layer infrared (IR) shielding configuration to reduce the effect of thermal radiation and demonstrate that improved shielding suppresses the quasiparticle-induced parity-switching rate. The effective qubit temperature follows the phonon bath down to 17 mK, enabling initialization errors of ∼ 0.01% for 3 GHz qubits without any reset metrics.
In the second work, we systematically investigate ng-dependent MIST dynamics governed by the diabaticity and symmetry of pulse shaping of a charge-sensitive transmon architecture. We engineer fast-load and fast-clear pulses that selectively suppress resonator photon overshoots, thereby demonstrating a practical strategy to mitigate MIST without requiring complex waveforms or real-time feedback. Utilizing active gate-voltage control and rapid feedback, the MIST probability is precisely mapped against ng and the steady-state resonator photon number, demonstrating a concrete agreement with numerical Floquet branch analysis. Lastly, 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.
These results show a great improvement in superconducting transmon qubit readout. Allowing us to start with a high readout fidelity as a great starting point in qubit operation.
References:
- W.-E. Lin, L.-C. Hsiao, C.-H. Ma, E.-H. Yeh, W.-L. Peng, H.-S. Goan, C.-S. Wu, Y.-N. Chen, Y.-F. Chen#, C.-T. Ke#, C.-D. Chen, “Mitigation of Measurement-Induced State Transitions via a Fast-Load and Fast-Clear Readout” arXiv:2607.23681v1 (2026).
- W.-E. Lin, C.-H. Ma, E.-H. Yeh, W.-L. Peng, Y.-S. Wei, H.-S. Goan, C.-S. Wu, C.-T. Ke#, Y.-F. Chen#, C.-D. Chen, “Suppression of Quasiparticle Poisoning to 10−11 Levels in Superconducting Qubits via Infrared Shielding” arXiv:2606.07339 (2026).