Tensor-network simulation of strongly coupled multi-fluxonium circuits

arXiv:2611.05627v1 Announce Type: new Abstract: Designing a superconducting quantum processor rests on predicting the low-lying spectrum of its coupled circuit. The Hilbert-space dimension of the circuit's lumped-element model grows exponentially with the number of circuit nodes. The usual methods split the circuit into subsystems, but that split is hard to choose when the elements are strongly coupled. We present a tensor-network method that chooses no subsystems and whose memory and run time per solve are set by the number of modes and two truncations, the Fock cutoff of each normal mode and the bond dimension of a matrix product state (MPS), not by the Hilbert-space dimension.