1. Institute of Industrial Science and Institute
for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
2. Advanced Institute for Materials
Research (AIMR), Tohoku University, Sendai
980-8577, Japan
3. CREST-Japan Science and Technology Agency, Kawaguchi,
Saitama 332-0012, Japan