High-fidelity transmon-coupler-activated CCZ gate on fluxonium qubits

The Toffoli gate takes a special place in the quantum information theory. It opens up a path for efficient implementation of complex quantum algorithms. Despite tremendous progress of the quantum processors based on the superconducting qubits, realization of a high-fidelity three-qubit operation is still a challenging problem. Here, we propose a way to perform a high-fidelity CCZ gate on fluxoniums capacitively connected via a transmon qubit, activated by a microwave pulse on the coupler. The main advantages of the approach are relative quickness, simplicity of calibration and significant suppression of the unwanted longitudinal ZZ interaction. We provide numerical simulation of a 95-ns-long gate of higher than 99. 99% fidelity with realistic circuit parameters in the noiseless model and estimate an error of about 0. 25% under the conventional decoherence rates.