Figure 1

Circuit diagram of two charged qubits (green) coupled through a grounded SQUID (blue). \(E_{J_{1(2)}}\), \(C_{J_{1(2)}}\), \(C_{g_{1(2)}}\), and \(V_{g_{1(2)}}\) are the Josephson energy, Josephson capacitance, gate capacitance, and gate voltage of the qubit 1(2) respectively. \(E_{J_{s}}\) and \(C_{s}\) are the Josephson energy and effective capacitance of the SQUID. Moreover, \(C_{c}\) is the coupling capacitance, and \(\Phi _{1}\), \(\Phi _{2}\), and \(\Phi _{s}\) are node fluxes that define the degrees of freedom of the circuit