Trapped Ion Heating from Correlated Motion of Electrode Adsorbates

Trapped ion qubits are plagued by a phenomenon called “anomalous heating,” where motional modes of the ion are excited by the environment causing decoherence of the encoded quantum information. Evidence suggests the origin of this heating is associated with the surface of the trapping electrodes. In this work, we combine first-principles electronic structure calculations, molecular dynamics simulations, and master equations to explore the role of high densities of adsorbed molecules on the electrode surface as a potential source of trapped ion heating. Weakly adsorbed molecules interact with the metallic surface and acquire an induced dipole, which can couple to the ion, causing electric field noise. When a large density of adsorbates are present, on the order of a monolayer, their collective vibrational motion can create non-trivial frequency-dependent electric field noise and thus ion heating. We analyze the coverage dependence of this effect for different possible electrode adsorbates.