The race for quantum supremacy isn't just between tech companies, but between nation-states as well. Why it matters: The first country to produce effective, working quantum computers will have a key advantage in economics, defense and cybersecurity — and the U.S., China, and Europe are all competing. What's happening: Last month, the Commerce Department added a dozen Chinese companies to a trade blacklist in an effort to prevent emerging U.S. technologies from being used for quantum computing efforts that would boost Beijing's military. It was the latest move in a tech trade war between Washington and Beijing that has national…