Fast fluxonium readout with photon pumping and bath engineering

Fluxonium-based circuits, a leading quantum computing platform, continue to face the challenge of achieving rapid and high-fidelity readout. In this work, we propose a novel, experimentally viable readout scheme based on photon pumping. The geometric pumping transfers energy between a periodic flux drive and output photonic states via a higher-order filter, with energy transfer direction governed by the fluxonium qubit’s basis state. By filtering out the leakage transition and preserving the qubit transition frequency, we probe the potential to improve readout while maintaining the robustness central to quantum geometry. Furthermore, as large photon numbers and ultra-strong coupling are desirable to avoid strong qubit entanglement in readout with geometric pumping, our scheme enables multiple photon frequencies to simultaneously measure the qubit with high subspace purity. We suggest that this readout scheme could pave the way for fast, high-fidelity readout in quantum computing.