[1] Univ Tokyo, Inst Nano Quantum Informat Elect, Meguro Ku, 4-6-1 Komaba, Tokyo 1538505, Japan
[2] Univ Tokyo, Inst Ind Sci, Meguro Ku, 4-6-1 Komaba, Tokyo 1538904, Japan
[3] Tech Univ Munich, Walter Schottky Inst, Coulombwall 4, D-85748 Garching, Germany
[4] Bayer Akad Wissensch, Walther Meissner Inst, D-85748 Garching, Germany
[5] Tech Univ Munich, Phys Dept, D-85748 Garching, Germany
[6] Univ Autonoma Madrid, Condensed Matter Phys Ctr IFIMAC, E-28049 Madrid, Spain
[7] Russian Quantum Ctr, Novaya 100, Skolkovo 143025, Moscow Region, Russia
[8] Univ Basque Country UPV EHU, Dept Phys Chem, Apartado 644, E-48080 Bilbao, Spain
[9] Basque Fdn Sci, Ikerbasque, Maria Diaz Haro 3, E-48013 Bilbao, Spain
[10] Stanford Univ, Ginzton Lab, Stanford, CA 94305 USA