1. NTT Device Technology Laboratories NTT Corporation 3-1, Morinosato Wakamiya Atsugi-shi Kanagawa 243-0198 Japan
2. NTT Device Innovation Center NTT Corporation 3-1, Morinosato Wakamiya Atsugi-shi Kanagawa 243-0198 Japan
3. Research Institute of Electrical Communication Tohoku University Katahira 2-1-1, Aoba-ku Sendai 980-8577 Japan