Robust multimode superconducting circuit optimized for quantum information processing

Multimode superconducting circuits offer a promising platform for engineering robust systems for quantum computation. Previous studies indicate that single-mode devices cannot be engineered to simultaneously exhibit resilience against multiple decoherence sources due to conflicting requirements. In contrast, multimode systems offer increased flexibility and have proven capable of overcoming these fundamental limitations. Here, we present a multimode device optimized for quantum information processing. It features an anharmonicity of a third of the qubit frequency and reduced energy dispersion caused by charge and magnetic flux fluctuations. It exhibits improvements over the fundamental errors limiting transmon and fluxonium coherence and control, achieving ratios between the total coherence time and the gate time T 2 / t g one order of magnitude larger than transmon and two times larger than fluxonium for microwave charge drives, assuming equal dielectric and inductive loss quality factors and limited drive strength. Simulations further demonstrate the device’s robustness to circuit parameter deviations, a known limitation of many multimode devices.