Power-efficient all-microwave manipulation of superconducting qubits with a fixed-frequency transmon coupler

The fixed-frequency transmon system is a promising candidate for practical quantum processor thanks to its long coherence time and low wiring cost. However, such architecture requires all-microwave entangling gates enabled with precise qubit-frequency allocation, which is a significant burden on design and fabrication. To address this issue, we propose and experimentally demonstrate a novel power-efficient all-microwave entangling gate using a fixed-frequency transmon coupler. This scheme, which tolerates relatively large frequency variations of qubits, executes a controlled-Z gate with 97.7(2)% average fidelity and eliminates residual ZZ interaction.