1. School of Fundamental Science and Technology, Keio University 1 , Yokohama, Kanagawa 223-8522, Japan
2. Center for Spintronics Research Network, Keio University 2 , Yokohama, Kanagawa 223-8522, Japan
3. Research Center for Emerging Computing Technologies, National Institute of Advanced Industrial Science and Technology (AIST) 3 , Tsukuba, Ibaraki 305-8568, Japan
4. NEC-AIST Quantum Technology Cooperative Research Laboratory, National Institute of Advanced Industrial Science and Technology (AIST) 4 , Tsukuba, Ibaraki 305-8568, Japan
5. Nanomaterials Research Institute, Kanazawa University 5 , Kanazawa, Ishikawa 920-1192, Japan
6. Device Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) 6 , Tsukuba, Ibaraki 305-8568, Japan
7. Institute for Chemical Research, Kyoto University 7 , Uji, Kyoto 611-0011, Japan
8. Center for Spintronics Research Network, Kyoto University 8 , Uji, Kyoto 611-0011, Japan
9. International Center for Quantum-field Measurement Systems for Studies of the Universe and Particles (QUP), KEK 9 , Tsukuba, Ibaraki 305-0801, Japan
10. Department of Physics, The University of Tokyo 10 , Bunkyo-ku, Tokyo 113-0033, Japan