  We propose an implementation of the two-qubit gate in a quantum dot spin
qubit system which is immune to charge noise problems. Our proposed
implementation, if it could be realized in a physical system, would have the
advantage of being robust against uncertainties and fluctuations in the tunnel
coupling and barrier gate voltage pulse area. The key idea is to introduce an
auxiliary dot and use an analog to the stimulated Raman adiabatic passage pulse
sequence in three-level atomic systems, often referred to in the context of
electron transport in quantum dot systems as Coherent Tunneling by Adiabatic
Passage. Spin-dependent tunneling opens the possibility of performing two-qubit
gate operations by this method.
