1. Institute for Physics of Microstructures of the Russian Academy of Sciences and Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod 603950, Russia
2. Department of Computer Science and Engineering, University of Aizu, Aizuwakamatsu, Fukushima 965-8580, Japan
3. Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan