China has been investing billions in nuclear fusion research. A potential game-changer for global energy, fusion has been slow to live up to promises, but now, Chinese scientists have reported yet another breakthrough in the process: a state of matter that was previously only theorized. Reported in Science Advances, the breakthrough consisted in overcoming a limit in electron density that, if breached, disrupts the operation of the tokamak—the installation where fusion occurs. In a sense, the achievement appears to be one more obstacle cleared…