Structures with Vertically Stacked Ge/Si Quantum Dots for Logical   Operations
  Ge/Si structures with vertically stacked quantum dots are simulated to implement the basic elements of a quantum computer for operation with electron spin states. Elastic-strain fields are simulated using the conjugate gradient method and an atomistic model based on the Keating potential. Calculations are performed in the cluster approximation using clusters containing about three million atoms belonging to 150 coordination spheres. The spatial distributions of the strain energy density and electron potential energy are calculated for different valleys forming the bottom of the silicon conduction band. It is shown that the development of multilayer structures with vertically stacked quantum dots makes it possible to fabricate deep potential wells for electrons with vertical tunnel coupling. 
Yu. N. Morokov, M. P. Fedoruk, A. V. Dvurechenskii, A. F. Zinov'eva,   and A. V. Nenashev
cond-mat.mes-hall