1. Department of Nuclear Engineering; Kyoto University; Sakyo Kyoto 606-8501 Japan
2. JEOL Ltd; Tokyo Japan
3. CREST; Japan Science and Technology Agency (JST); Chiyoda Tokyo 102-0075 Japan
4. Department of Electronic Science and Engineering; Kyoto University; Nishikyo Kyoto 615-8510 Japan
5. Quantum Science and Engineering Center; Kyoto University; Uji Kyoto 611-0011 Japan