Realization of adiabatic and diabatic CZ gates in superconducting qubits coupled with a tunable coupler

High fidelity two-qubit gates are fundamental for scaling up the superconducting qubit 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 diabatic methods. The Clifford based randomized benchmarking (RB) method is used to assess and optimize the CZ gate fidelity. The fidelities of adiabatic and diabatic CZ gates are 99.53(8)% and 98.72(2)%, respectively. We also analyze the errors induced by the decoherence. Comparing to 30 ns duration time of adiabatic CZ gate, the duration time of diabatic CZ gate is 19 ns, revealing lower incoherence error rate r(incoherent,int)' = 0.0197(5) compared to r(incoherent,int) = 0.0223 (3).

Automated summary

The study utilizes a frequency-tunable coupler to connect two qubits and demonstrates CZ gate using both adiabatic and diabatic methods. Clifford based randomized benchmarking method is employed to assess and optimize gate fidelity, with adiabatic CZ gate achieving a higher fidelity compared to diabatic CZ gate. Additionally, analysis of errors induced by decoherence reveals lower incoherence error rate in diabatic CZ gate compared to adiabatic CZ gate.