How did Google's AlphaZero beat the world's best chess computer?

Google’s AlphaZero, after just four hours of training, last week trounced the highest rated chess engine in the world, Stockfish. How did it do this? 

AI Taught Itself to Be the Best Chess Player in the World—What's

Google's AI Chess Engine Alpha Zero inspired me to become an avid

Checkmate: how we mastered the AlphaZero cover, Science

How the Artificial Intelligence Program AlphaZero Mastered Its

AlphaZero, Vladimir Kramnik and reinventing chess

AlphaZero: the new king of chess - De Econometrist

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AI beats AI: AlphaZero becomes the best game player in history

AI Taught Itself to Be the Best Chess Player in the World—What's

Google's AlphaZero AI mastered chess in just four hours