1. Quantum Science and Engineering Center; Kyoto University; Gokasho, Uji Kyoto 611-0011 Japan
2. Institute of Multidisciplinary Research for Advanced Materials; Tohoku University; Katahira, 2-1-1, Aoba-ku Sendai Miyagi 980-8577 Japan
3. JEOL Ltd.; 3-1-2, Musashino, Akishima Tokyo 196-8558 Japan
4. SENTAN, Japan Science and Technology Agency (JST); Chiyoda Tokyo 102-0075, Japan