Charge- and Flux-Insensitive Tunable Superconducting Qubit
Eyob Alebachew Sete, Matthew J. Reagor, Nicolas Didier, Chad T. Rigetti · Physical Review Applied · 2017
A central challenge in building a scalable quantum computer with superconducting qubits is simultaneously achieving long coherence times and fast two-qubit gates. Currently, fast (tunable) gates are obtained at the expense of coherence time. The authors propose a ``flatsonium'' qubit, based on the highly nonlinear fluxonium qubit, that yields both coherence and tunability---jackpot. Dephasing due to global flux noise is reduced by engineering flux-insensitive sweet spots in the qubit spectrum at the frequencies of interest, while leakage errors are eliminated by the typically large anharmonicity of its energy spectrum.