Superconducting fluxonium qubits provide a promising alternative to transmons on the path toward large-scale superconductor-based quantum computing due to their better coherence and larger anharmonicity. A major challenge for multi-qubit fluxonium devices is the experimental demonstration of a scalable crosstalk-free multi-qubit architecture with high fidelity single-qubit and two-qubit gates, single-shot readout and state initialization. Here, we present a two-qubit fluxonium-based quantum processor with a tunable coupler element following our theoretical proposal [DOI: 10.1063/5.0064800]. We experimentally demonstrate fSim-type and controlled-Z gates with 99.55% and 99.23% fidelities, respectively. The residual ZZ interaction is suppressed down to the few kHz level. Using a galvanically coupled flux control line, we implement high fidelity single-qubit gates and ground state initialization with a single arbitrary waveform generator channel per qubit.
@article{arxiv.2203.16302,
title = {High fidelity two-qubit gates on fluxoniums using a tunable coupler},
author = {Ilya N. Moskalenko and Ilya A. Simakov and Nikolay N. Abramov and Alexander A. Grigorev and Dmitry O. Moskalev and Anastasiya A. Pishchimova and Nikita S. Smirnov and Evgeniy V. Zikiy and Ilya A. Rodionov and Ilya S. Besedin},
journal= {arXiv preprint arXiv:2203.16302},
year = {2022}
}