Scalable Quantum Processor Based on Superconducting Fluxonium Qubits

Superconducting circuits are among the most promising platforms for quantum computing. The milestone experiments demonstrating quantum advantage and suppression of quantum errors have already been performed on a simple and reliable transmon qubit. However, a transmon has a number of structural and technological features which limit the fidelity of basic operations required for a high-performance quantum computing device. Therefore, alternative superconducting qubits with a better protection from external noise are of growing interest. A fluxonium, which is characterized by significant anharmonicity and a large coherence time, is one of the most promising qubits. In this work, we describe the first experiments with an elementary unit cell of a quantum processor with planar fluxonium qubits. Methods of individual initialization and dispersive readout of qubits are demonstrated; single-qubit gates with a fidelity exceeding 99.96% and a two-qubit CZ gate with a fidelity of 99.22% are realized.