1. Graduate School of Engineering Science Osaka University Osaka 560‐8531 Japan
2. Department of Physics Faculty of Science Shinshu University Nagano 390‐8621 Japan
3. Department of Electronic Science and Engineering Kyoto University Kyoto 615‐8510 Japan
4. School of Engineering Tokai University Kanagawa 259‐1292 Japan
5. Center for Quantum Information and Quantum Biology Osaka University Osaka 560‐8531 Japan