  A scheme based on Coherent Tunneling by Adiabatic Passage (CTAP) of
exchange-only spin qubit quantum states in a linearly arranged double quantum
dot chain is demonstrated. Logical states for the qubit are defined by adopting
the spin state of three electrons confined in a double quantum dot. The
possibility to obtain gate operations entirely with electrical manipulations
makes this qubit a valuable architecture in the field of quantum computing for
the implementation of quantum algorithms. The effect of the external control
parameters as well as the effect of the dephasing on the coherent tunneling in
the chain is studied. During adiabatic transport, within a constant energy
degenerate eigenspace, the states in the double quantum dots internal to the
chain are not populated, while transient populations of the mixed states in the
external ones are predicted.
