Understanding and mitigating decoherence in fluxonium qubits

The fluxonium qubit, with its long coherence time and large anharmonicity, is a promising candidate for the physical realization of quantum computation. State-of-the-art devices have achieved a relaxation time (T₁) and a coherence time (T₂) in the millisecond regime, and various decoherence mechanisms have been studied. We present experimental results from an tunable-E_J device to study dissipation in fluxonium qubits, using high-bandwidth flux controls to tune the device and measure the relaxation time in a large parameter space. We then analyze the data to characterize the noise spectrum and identify dissipation sources such as tunneling two-level systems and quasiparticles. Statistics and temporal fluctuations of coherence times in fixed-E_J devices will also be discussed. This work deepens our understanding of decoherence and enables its mitigation, thus paves the way for the implementation of high-fidelity fluxonium quantum processors.