Qubits Coupling via Lamped Element Resonators toward Quantum Annealing on Superconducting Circuit

We propose a coupling method of superconducting qubits for a novel quantum annealing circuit. In order to derive the capability of the quantum annealing system, a qubit is desirable to be coupled not only with adjacent qubits but also with other qubits located far apart. In this talk, we show a circuit that uses a lumped element resonator coupled with one qubit. The resonator-qubit units are coupled by SQUID-base couplers. Unlike the coplanar type resonator, the lumped element resonator can realize a uniform coupling strength independent of the position of the coupling. Therefore, it is possible to integrate circuits in a small space. By using rf - SQUID as a nonlinear inductor for coupling between resonators, it is possible to achieve ON / OFF and positive / negative intensity. Combining the unit and the nonlinear inductance is a new kind of scalable circuit scheme. Moreover, by strengthening the coupling between the resonator and the qubit, it is considered that the effective coupling strength between the qubits could be set to several hundred MHz.