Tunable inductive coupling of superconducting qubits in the strongly nonlinear regime

Understand

For a variety of superconducting qubits, tunable interactions are achieved through mutual inductive coupling to a coupler circuit containing a nonlinear Josephson element.

• In this paper we derive the general interaction mediated by such a circuit under the Born-Oppenheimer Approximation.
• This interaction naturally decomposes into a classical part, with origin in the classical circuit equations, and a quantum part, associated with the coupler's zero-point energy.
• Our result is non-perturbative in the qubit-coupler coupling strengths and in the coupler nonlinearity.