Realisation of adiabatic and di-adiabatic CZ gates in superconducting qubits coupled with a tunable coupler

  1. Huikai Xu,
  2. Weiyang Liu,
  3. Zhiyuan Li,
  4. Jiaxiu Han,
  5. Jingning Zhang,
  6. Kehuan Linghu,
  7. Yongchao Li,
  8. Mo Chen,
  9. Zhen Yang,
  10. Junhua Wang,
  11. Teng Ma,
  12. Guangming Xue,
  13. Yirong Jin,
  14. and Haifeng Yu
High fidelity two-qubit gates are fundamental for scaling up the superconducting number. We use two qubits coupled via a frequency-tunable coupler which can adjust the coupling strength, and demonstrate the CZ gate using two different schemes, adiabatic and di-adiabatic methods. The Clifford based Randomized Benchmarking (RB) method is used to assess and optimize the CZ gate fidelity. The fidelity of adiabatic and di-adiabatic CZ gates are 99.53(8)% and 98.72(2)%, respectively. We also analyze the errors induced by the decoherence, which are 92% of total for adiabatic CZ gate and 46% of total for di-adiabatic CZ gates. The adiabatic scheme is robust against the operation error. But the di-adiabatic scheme is sensitive to the purity and operation errors. Comparing to 30 ns duration time of adiabatic CZ gate, the duration time of di-adiabatic CZ gate is 19 ns, revealing lower incoherence error rincoherent,Clfford = 0.0197(5) than r′incoherent,Clfford = 0.0223(3).
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