How to Protect Superconducting Qubits from Environmental Noise

Superconducting qubits offer long coherence times relative to their operation speed, making them leading candidates for quantum computation. Unlocking their full potential requires both efficient control and protection from environmental noise. To enhance their quantum processing capabilities, we have improved fabrication processes to suppress intrinsic noise sources, achieving high quality factors with coherence times of several hundred microseconds. To protect the qubits from external noise we have investigated a control setup for superconducting fluxonium qubits that eliminates qubit decay through the control channel by adding a low-pass filter on the flux line. Still, we maintain coherent control of the qubit with a multi- photon drive scheme and reach single-qubit gate fidelities exceeding 99.94%. We have further developed a novel multi-mode qubit design - the P-mon - that allows us to decouple the qubit from the readout circuit and thus from photon-induced dephasing and Purcell- induced decay. Together, these advances bring us closer to building robust, noise-resilient superconduct-