[1] Japan Sci & Technol Agcy, ICORP, Quantum Spin Informat Project, Atsugi, Kanagawa 2430198, Japan
[2] NTT Corp, NTT Basic Res Labs, Atsugi, Kanagawa 2430198, Japan
[3] Tokyo Inst Technol, Mat & Struct Lab, Yokohama, Kanagawa 2268503, Japan
[4] Japan Sci & Technol Agcy, PRESTO, Kawaguchi, Saitama 3320012, Japan
[5] Univ Tokyo, Dept Appl Phys, Bunkyo Ku, Tokyo 1138656, Japan
[6] Univ Tokyo, Inst Nano Quantum Informat Elect, Meguro Ku, Tokyo 1538505, Japan