Spectroscopy and logic gates in a strongly coupled two-fluxonium device

The fluxonium is one of the leading candidates as an upgrade to the mainstream transmon qubits in large-scale superconducting quantum processors: With stronger anharmonicity, longer coherence times and the ability to engineer selection rules, it has the qualities to in principle deliver better logic gate fidelity than transmons. Towards validating fluxonium as a viable qubit for scaling up, it is essential to go from one fluxonium to two or more; yet two coupled fluxoniums in various coupling regimes still remain to be better explored. Our experimental study focuses on two fluxonium qubits under strong capacitive coupling and we analyze the hybridization of computational states and higher excited states as a function of external flux bias. We also show that the ZZ coupling between two fluxonium qubits makes it straightforward to realize single and two qubit operations and report our progress on benchmarking single and two qubit gates.