Modifications to the Proposed QC Architecture
Important new ideas:
1.   Quantum computing can proceed purely by
   Exchange (Heisenberg) interactions.
2. Free electrons may be good carriers of
   quantum information.
SiGe electron spin quantum computing (Vrijen, Yablonovitch).
B. E. Kane, Fortschritte der Physik 48, 1023 (2000).
Also on LANL archive.