Diffusion of carbon adatoms on gold ion trap electrode surfaces

In ion traps, the electric field noise emanating from the trap electrodes remains as a major obstacle to the realization of ion-trap based scalable quantum computing architectures. The source of this anomalous noise has been identified as the fluctuating surface adatom dipoles (mostly carbon-bearing). The original microscopic theory of fluctuating surface dipoles is static. In order to provide a more realistic picture of the surface dynamics, the mobility of these dipoles whose magnitude change with motion on the electrode surface should also be considered. One of the unknown parameters in the electric field noise spectral power is the diffusion constant of such adsorbates. In this study, classical molecular dynamics (MD) simulations are used to calculate long-time diffusion constant and transition rates of carbon adatoms on various gold surface orientations. The resultant fluctuation in the induced dipole moment is then obtained by computing the work function of the surface, using the density-functional theory method. Such time domain calculations also provide us with a clear picture of carbon structure and cluster formation on various gold surfaces.