1. Institute for Nano Quantum Information Electronics, and Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
2. Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi-shi 243-0197, Japan
3. NEC Corporation, 34 Miyukigaoka, Tsukuba-shi, Ibaraki 305-8501 Japan
4. National Institute of Information and Communications Technology, 588-2, Iwaoka, Nishi-ku, Kobe, Hyogo 651-2492, Japan
5. National Institute of Information and Communications Technology, 4-2-1, Nukui-Kitamachi, Koganei, Tokyo 184-8795, Japan
6. National Institute for Materials Science, 1-1, Namiki, Tsukuba-shi, Ibaraki 305-0044, Japan