1. Centre
for Quantum Computation and Communication Technology, School of Physics, The University of Sydney, Sydney, NSW 2006, Australia
2. Department
of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNano), Aarhus University, 8000 Aarhus C, Denmark
3. Measurement
Science and Standards, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
4. Institut National de la Recherche Scientifique, Énergie, Matériaux et Télécommunications, Varennes, Québec J3X 1S2, Canada
5. Nanochemistry
Research Institute and Discipline of Physics and Astronomy, Curtin University, GPO
Box U1987, Perth WA 6845, Australia