Fast CZ Gate via Energy-Level Engineering in Superconducting Qubits with a Tunable Coupler

  1. Benzheng Yuan,
  2. Chaojie Zhang,
  3. Chuanbing Han,
  4. Shuya Wang,
  5. Peng Xu,
  6. Huihui Sun,
  7. Qing Mu,
  8. Lixin Wang,
  9. Bo Zhao,
  10. Weilong Wang,
  11. and Zheng Shan
In superconducting quantum circuits, decoherence errors in qubits constitute a critical factor limiting quantum gate performance. To mitigate decoherence-induced gate infidelity, rapid implementation of quantum gates is essential. Here we propose a scheme for rapid controlled-Z (CZ) gate implementation through energy-level engineering, which leverages Rabi oscillations between the |11> state and the superposition state in a tunable-coupler architecture. Numerical simulations achieved a 17 ns nonadiabatic CZ gate with fidelity over 99.99%. We further investigated the performance of the CZ gate in the presence of anharmonicity offsets. The results demonstrate that a high-fidelity CZ gate with an error rate below 10^-4 remains achievable even with finite anharmonicity variations. Furthermore, the detrimental impact of spectator qubits in different quantum states on the fidelity of CZ gate is effectively suppressed by incorporating a tunable coupler. This scheme exhibits potential for extending the circuit execution depth constrained by coherence time limitations.
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