Fluxonium Qubit Design and EPR analysis

Fluxonium qubits promise a better, alternative solution for large-scale quantum computing in terms of lower error rates. Compared to the conventional transmon qubit, the fluxonium is realized with just one more element: a linear inductor. It is essential to have the Hamiltonian parameters of the device before the fabrication steps since numerical simulations guide the design process and can help in understanding and interpreting measurement results. State-of-the-art analysis of superconducting quantum circuits uses the energy participation ratio (EPR) method which extracts linear terms from finite element simulations and adds non-linear (quantum) terms using the energy participations extracted from the classical simulations. We designed and simulated a fluxonium qubit using IBM Qiskit-metal, which includes open-source code for EPR analysis. We also developed the EPR analysis library to treat the non-linear terms non-perturbative allowing for analysis beyond weakly anharmonic qubits. In this talk, I will show our design and simulation results. Moreover, I will extract the Hamiltonian for a fluxonium qubit and readout resonator and compare the simulation results with the measurement results.