A Laser-cooled Single-atom-on-demand Source For Si Quantum Computing.

A promising proposal by B. Kane for a scalable silicon quantum computer requires the placement of 31P atoms 20 nm apart and 10 nm below the surface in pure 28Si to 1 nm precision. This paper presents progress on a scheme for laser cooling and trapping single 31Si atoms in a magneto-optical trap (MOT), resonantly ionizing that one atom near threshold, and softly depositing the single 31Si+ ion in Si to nm precision at ∼100 eV. A few hours after deposition, 31Si beta decays to 31P+. The hyperfine structure and isotope shifts of the 221.7 nm cooling transition for the stable isotopes of Si have been measured with precision for the first time. Sufficient power for the MOT at this wavelength has also been demonstrated. New autoionizing states near threshold have been found and ionization cross sections determined. The velocity distributions of laser ablated Si atoms have been measured, and unexpected results have been found. Construction of the MOT and design of the ion optics are underway. [ABSTRACT FROM AUTHOR]