Understanding and mitigating decoherence in fluxonium qubits – Dephasing

The fluxonium qubit is a promising candidate for the physical realization of quantum computation on the superconducting circuits platform. State-of-the-art devices have achieved relaxation time (T₁) and coherence time (T₂) of several hundred microseconds, but the reported T₂ in the literature for various parameter regimes and flux biases has not reached the limit of 2T₁. We present theoretical models and experimental data to study dephasing mechanisms in fluxonium qubits. Statistics and temporal fluctuations in measured data are analyzed to reveal the impact of environmental noise on device performance at different time scales. We will discuss the choice of device parameters, the characterization and suppression of noise levels, and the strategies for mitigating dephasing mechanisms. The improvement of coherence time paves the way for high-fidelity gate operations in fluxonium-based quantum processors.