  There are several known schemes for entangling trapped ion quantum bits for
large-scale quantum computation. Most are based on an interaction between the
ions and external optical fields, coupling internal qubit states of
trapped-ions to their Coulomb-coupled motion. In this paper, we examine the
sensitivity of these motional gate schemes to phase fluctuations introduced
through noisy external control fields, and suggest techniques to suppress the
resulting phase decoherence.
