Dephasing in Fluxonium Qubits from Coherent Quantum Phase Slips*

Recent experiments on fluxonium qubits in planar circuit architectures have demonstrated near-record coherence times and gate fidelities. In order to improve these metrics further, we seek to develop a holistic model of decoherence in fluxonium qubits. Here we focus on one dephasing mechanism inherent to Josephson junction arrays which arises from the Aharonov-Casher effect and can limit fluxonium coherence times in circuits with large superinductors. In this talk, we report coherence times in fluxonium qubits specifically engineered to be sensitive to this dephasing mechanism and compare with theoretical models.