1. RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan, PRESTO, Japan Science and Technology Corporation, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan, and Department of Knowledge-Based Information Engineering, Toyohashi University of Technology, 1-1 Tempaku, Toyohashi, Aichi 441-8580, Japan