Tensor-network diagonalization of many-body superconducting qubits

We introduce a tensor-network method tailored to the simulation of large-scale superconducting quantum circuits. We leverage information unavailable to other state-of-the-art numerical techniques to produce first-principles coherence-time estimates for the fluxonium qubit. In particular, we study the charge dispersion of this qubit due to coherent quantum phase slip processes. Taking advantage of this novel approach, we present direct numerical evidence of the validity of the effective theory introduced in [V. E. Manucharyan et. al, PRB 85, 024521 (2012)].