Yuta Hirasaki

Dynamics of measurement-induced state transitions in superconducting qubits

  1. Yuta Hirasaki,
  2. Shunsuke Daimon,
  3. Naoki Kanazawa,
  4. Toshinari Itoko,
  5. Masao Tokunari,
  6. and Eiji Saitoh
We have investigated temporal fluctuation of superconducting qubits via the time-resolved measurement for an IBM Quantum system. We found that the qubit error rate abruptly changes
during specific time intervals. Each high error state persists for several tens of seconds, and exhibits an on-off behavior. The observed temporal instability can be attributed to qubit transitions induced by a measurement stimulus. Resonant transition between fluctuating dressed states of the qubits coupled with high-frequency resonators can be responsible for the error-rate change.
arxiv pdf

Detection of temporal fluctuation in superconducting qubits for quantum error mitigation

  1. Yuta Hirasaki,
  2. Shunsuke Daimon,
  3. Toshinari Itoko,
  4. Naoki Kanazawa,
  5. and Eiji Saitoh
We have investigated instability of a superconducting quantum computer by continuously monitoring the qubit output. We found that qubits exhibit a step-like change in the error rates.
This change is repeatedly observed, and each step persists for several minutes. By analyzing the correlation between the increased errors and anomalous variance of the output, we demonstrate quantum error mitigation based on post-selection. Numerical analysis on the proposed method was also conducted.
arxiv pdf