CANCELLATION OF UNWANTED INTERACTIONS IN A SUPERCONDUCTING QUANTUM ARCHITECTURE

A quantum circuit called a “qumon” is provided to cancel unwanted ZZ interaction in a superconducting qubit architecture. The qumon qubit has a high coherence, and a positive anharmonicity that may be tuned to cancel the negative anharmonicity in a coupled qubit, such as a transmon qubit. The qumon has three parallel branches, in which are a shunt capacitor; a Josephson junction having weighted energy level and capacitance; and several Josephson junctions in series. The weight is chosen to provide the desired anharmonicity, and the transverse flux noise and transverse charge noise each decrease in proportion to the number of the Josephson junctions in series. Because unwanted ZZ interactions are canceled, qumon qubits and transmon qubits may be capacitively coupled in an alternating pattern to provide a surface code in which these interactions are canceled in an extensible way.