  Many efforts are currently underway to build a device capable of large scale
quantum information processing (QIP). Whereas QIP has been demonstrated for a
few qubits in several systems, many technical difficulties must be overcome in
order to construct a large-scale device. In one proposal for large-scale QIP,
trapped ions are manipulated by precisely controlled light pulses and moved
through and stored in multizone trap arrays. The technical overhead necessary
to precisely control both the ion geometrical configurations and the laser
interactions is demanding. Here we propose methods that significantly reduce
the overhead on laser beam control for performing single and multiple qubit
operations on trapped ions. We show how a universal set of operations can be
implemented by controlled transport of ions through stationary laser beams. At
the same time, each laser beam can be used to perform many operations in
parallel, potentially reducing the total laser power necessary to carry out QIP
tasks. The overall setup necessary for implementing transport gates is simpler
than for gates executed on stationary ions. We also suggest a transport-based
two-qubit gate scheme utilizing microfabricated permanent magnets that can be
executed without laser light.
