H. Bernien, B. Hensen, W. Pfaff, G. Koolstra, M.S. Blok, L. Robledo, T.H. Taminiau, M. Markham, D.J. Twitchen, L. Childress, and R. Hanson ∗ Kavli Institute of Nanoscience Delft, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands Element Six Ltd., Kings Ride Park, Ascot, Berkshire SL5 8BP, United Kingdom McGill University Department of Physics, 3600 Rue University, Mo...