Inductive coupling scheme for quantum simulation with superconducting qubits

Superconducting qubits provides a promising platform for quantum simulation of Bose-Hubbard Hamiltonians due to the flexibility of tuning system parameters. Changing the ratio of on-site interaction strength due to qubit anharmonicity and coupling strength between qubits allows exploration of different quantum phases in the Bose-Hubbard model. Probing these quantum phase transitions requires the ability to dynamically tune the coupling strength. An inductive coupling scheme can make use of the nonlinearity of a Josephson junction to dynamically change the mutual inductance between two qubits by applying a DC magnetic flux [1]. The relative mutual inductances between the qubits and couplers can be engineered to achieve a large range of coupling strengths. Having both a high coupling strength and the ability to tune between positive and negative couplings enables quantum simulation experiments in various parameter regimes. We present our experimental realization and characterization of a tunable inductive coupler between transmon qubits.

[1] Geller et al., PRA 92, 012320 (2015)