1. Quantum Science and Engineering Center, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
2. Department of Physics, University of Kaiserslautern, 67663 Kaiserslautern, Germany
3. Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615−8510, Japan
4. Department of Nuclear Engineering, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
5. SENTAN, Japan Science and Technology Agency (JST), Chiyoda, Tokyo 102-0075, Japan