ABSTRACT
Electron and nuclear spins in semiconductors provide promising candi-
dates for qubits, but a large number of challenges must be overcome before
they may be effectively used for fast quantum information processing on a
large scale. Such qubits are always subject to some decoherence, and our
methods for controlling them are always imperfect. The development of
fault-tolerant architectures is critical for large-scale quantum communica-
tion networks and quantum computers. Most semiconductor-based schemes
for quantum logic rely on nearest-neighbor spin-spin couplings, based on
exchange or dipole-dipole couplings (for example, see Chapters 1 and 2).
Fault tolerant architectures with such schemes are possible, but make high
demands on error rates and result in low final computation speeds.
