Coupling superconducting flux qubits at optimal point via dynamic decoupling with the quantum bus

We propose a scheme with dc control of finite bandwidth to implement a two-qubit gate for superconducting flux qubits at the optimal point. We provide a detailed nonperturbative analysis on the dynamic evolution of the qubits interacting with a common quantum bus. An effective qubit-qubit coupling is induced while decoupling the quantum bus with proposed pulse sequences. The two-qubit gate is insensitive to the initial state of the quantum bus and applicable to nonperturbative coupling regime which enables rapid two-qubit operation. This scheme can be scaled up to multiqubit coupling.