  We provide a conceptual framework for developing a scalable topological
quantum computer. It relies on forming Majorana fermions using circular
electronic gates in two-dimensional p-wave superconductors. The gates allow the
precise control of the number, position, and dynamics of Majorana fermions.
Using an array of such gates, one can implement the full features of
topological quantum computation, including the braiding and fusion of Majoranas
in space-time. The gates serve two purposes: They modulate the chemical
potential locally to turn a topological superconductor into a normal conductor,
and they are used to move the Majoranas in space-time. With a perpendicular
magnetic field, the normal region localizes a quantum of magnetic flux. Under
these conditions, the boundary between the normal region and the
superconducting region supports a single zero-energy Majorana bound state. The
localized zero mode is sufficiently separate from other states and can be
dragged by sequentially applying voltages to the adjacent gates to implement
quantum computation. We briefly describe the fabrication process to construct
the device and determine key properties from experimentally determined
parameters. The digital qualities of topological protection provide intrinsic
immunity to the inevitable fabrication nonuniformities.
