  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.
