  We propose a novel scheme of solid state realization of a quantum computer
based on single spin "enhancement mode" quantum dots as building blocks. In the
enhancement quantum dots, just one electron can be brought into initially empty
dot, in contrast to depletion mode dots based on expelling of electrons from
multi-electron dots by gates. The quantum computer architectures based on
depletion dots are confronted by several challenges making scalability
difficult. These challenges can be successfully met by the approach based on
ehnancement mode, capable of producing square array of dots with versatile
functionalities. These functionalities allow transportation of qubits,
including teleportation, and error correction based on straightforward one- and
two-qubit operations. We describe physical properties and demonstrate
experimental characteristics of enhancement quantum dots and single-electron
transistors based on InAs/GaSb composite quantum wells. We discuss the
materials aspects of quantum dot quantum computing, including the materials
with large spin splitting such as InAs, as well as perspectives of enhancement
mode approach in materials such as Si.
