  Addressability of spin qubits in a silicon double quantum dot setup in the
(1,1) charge configuration relies on having a large difference between the
Zeeman splittings of the electrons. When the difference is not sufficiently
large, the rotating wave approximation becomes inaccurate. We consider a device
working in this regime, with always-on exchange coupling, and describe how a CZ
gate and arbitrary one-qubit gates which are robust against charge noise can be
implemented by smoothly pulsing the microwave source, while eliminating the
crosstalk. We find that the most significant deviations from the rotating wave
approximation, which are analogous to the Bloch-Siegert shift in a two-level
system, can be compensated using local virtual gates.
