Table 1.

Device parameters corresponding to the five-mode circuit in Fig. 3a

EJ/h	EC/h	EL/h	ϵL/h	ε	ELR/h	ELS/h	ϵC/h
3.98	10.40	0.57	6.16	0.033	18.03	11.91	3.24

The first seven parameters are found by fitting the spectral lines in Fig. 4a–h to the circuit Hamiltonian, with all capacitances (except junction capacitances) fixed to values from finite-element simulations (see Supplementary Information). The final parameter—the oscillator charging energy in the absence of the junctions—is computed from the full device capacitance matrix and is not found from the fit.