Superconducting quantum circuit

A superconducting quantum circuit comprising:

• first to fourth qubits;
• and
• a coupler that couples the first to fourth qubits with a four-body interaction,
• wherein the coupler includes:
• first and second electrodes arranged opposed to each other;
• and
• a nonlinear element including at least one Josephson junction and bridging the first and second electrodes,
• wherein each of the first to fourth qubits includes a resonator including:
• a loop circuit with a first superconducting line, a first Josephson junction, a second superconducting line and a second Josephson junction connected in a ring-shape;
• and
• a capacitor connected in parallel to the loop circuit,
• wherein the first and second qubits are capacitively coupled to the first electrode of the coupler, and
• the third and fourth qubits are capacitively coupled to the second electrode of the coupler, and
• wherein a magnitude relationship among a capacitance value C of a capacitive coupling between each of the first to fourth qubits and the coupler, a capacitance value CJ of the capacitor connected in parallel to the loop circuit of each of the first to fourth qubits, and a capacitance value Cg between the first and second electrodes of the coupler is set to CJ>Cg>C.