1. Department of Materials, Quantum Information Processing Interdisciplinary Research Collaboration, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
2. IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
3. Department of Chemistry and Institute for Advanced Research, Nagoya University, Furo-Cho, Chikusa-ku, Nagoya 464-8602, Japan