Exchange in a silicon-based quantum dot quantum computer architecture
  In bulk silicon, intervalley electronic interference has been shown to lead to strong oscillations in the exchange coupling between impurity electronic wavefunctions, posing a serious manufacturability problem for proposed quantum computers. Here we show that this problem does not arise in proposed architectures using Si/SiGe quantum dots because of the large in-plane strain in Si quantum wells together with the strong confinement potential typical of heterostructures. 
S.N. Coppersmith, Seungwon Lee, and Paul von Allmen