  One of the key pathways towards scalability of spin-based quantum computing
systems lies in achieving long-range interactions between electrons and
increasing their inter-connectivity. Coherent spin transport is one of the most
promising strategies to achieve this architectural advantage. Experimental
results have previously demonstrated high fidelity transportation of spin
qubits between two quantum dots in silicon and identified possible sources of
error. In this theoretical study, we investigate these errors and analyze the
impact of tunnel coupling, magnetic field and spin-orbit effects on the spin
transfer process. The interplay between these effects gives rise to double dot
configurations that include regimes of enhanced decoherence that should be
avoided for quantum information processing. These conclusions permit us to
extrapolate previous experimental conclusions and rationalize the future design
of large scale quantum processors.
