  We propose a scheme to couple two superconducting charge or flux qubits
biased at their symmetry points with unequal energy splittings. Modulating the
coupling constant between two qubits at the sum or difference of their two
frequencies allows to bring them into resonance in the rotating frame.
Switching on and off the modulation amounts to switching on and off the
coupling which can be realized at nanosecond speed. We discuss various physical
implementations of this idea, and find that our scheme can lead to rapid
operation of a two-qubit gate.
