  We describe in detail a set of ideas for implementing qubits, quantum gates
and quantum gate networks in a semiconductor heterostructure device. Our
proposal is based on an extension of the technology used for surface acoustic
wave (SAW) based single-electron transport devices. These devices allow single
electrons to be captured from a two-dimensional electron gas in the potential
minima of a SAW. We discuss how this technology can be adapted to allow the
capture of electrons in pure spin states and how both single and two-qubit
gates can be constructed using magnetic and non-magnetic gate technology. We
give designs for readout gates to allow the spin state of the electrons to be
measured and discuss how combinations of gates can be connected to make
multi-qubit networks. Finally we consider decoherence and other sources of
error, and how they can be minimized for our design.
