By ELLEN NAKASHIMA | The Washington Post | Published: April 8, 2021 WASHINGTON — The Biden administration on Thursday placed seven Chinese firms and government labs under U.S. export controls for their involvement in China's effort to build supercomputers that help develop nuclear and other advanced military weapons. All seven are linked to China's ambition to build the world's first exascale computer, Commerce Department officials said. An exascale computer — the next frontier in high-performance computing — can handle a million trillion calculations per second. That's the sort of s...