  We propose an architecture and methodology for large-scale quantum
simulations using hyperfine states of trapped-ions in an arbitrary-layout
microtrap array with laserless interactions. An ion is trapped at each site,
and the electrode structure provides for the application of single and pairwise
evolution operators using only locally created microwave and radio-frequency
fields. The avoidance of short-lived atomic levels during evolution effectively
eliminates errors due to spontaneous scattering; this may allow scaling of
quantum simulators based on trapped ions to much larger systems than currently
estimated. Such a configuration may also be particularly appropriate for
one-way quantum computing with trapped-ion cluster states.
