A>99.9%-fidelity quantum-dot spin qubit with coherence limited by charge noise

1 RIKEN Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan 2 Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan 3 JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan 4 Department of Physical Electronics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8552, Japan 5 Institute of Industrial Science, University of Tokyo, Meguro-ku, Tokyo 153-8505, Japan 6 Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan 7 Department of Applied Physics and Physico-Informatics, Keio University, Hiyoshi, Yokohama 223-8522,