Fig. 1: Circuit model of the fluxonium qubit.
From: Efficient modeling of superconducting quantum circuits with tensor networks
a Detailed circuit scheme including a “black-sheep” junction (center) shunted by a capacitance (top) and a junction-array superinductance with NJ junctions (bottom). Stray capacitances to ground are depicted in a lighter shade of blue. b Effective circuit in which the junction array is modeled as a linear inductance. ϕi for i ∈ [0, NJ] denotes the superconducting phase at every circuit node, while θi for i ∈ [1, NJ] is the phase difference at every junction of the array. The superinductance (or fluxonium) mode is defined as the phase difference across the black-sheep junction: \(\phi ={\phi }_{0}-{\phi }_{{N}_{{\rm{J}}}}=\mathop{\sum }\nolimits_{i = 1}^{{N}_{{\rm{J}}}}{\theta }_{i}\).
