  Oscillating magnetic fields and field gradients can be used to implement
single-qubit rotations and entangling multi-qubit quantum gates for trapped-ion
quantum information processing (QIP). With fields generated by currents in
microfabricated surface-electrode traps, it should be possible to achieve gate
speeds that are comparable to those of optically induced gates for realistic
distances between the ion crystal and the electrode surface.
Magnetic-field-mediated gates have the potential to significantly reduce the
overhead in laser beam control and motional state initialization compared to
current QIP experiments with trapped ions and will eliminate spontaneous
scattering, a fundamental source of decoherence in laser-mediated gates.
