Artificial intelligence has made history, for the first time beating humans at poker - the last remaining game in which humans had managed to maintain the upper hand.

Libratus, an artificial intelligence robot built by Carnegie Mellon University, racked up over $1.7 million worth of chips against four of the top professional poker players in the world in a 20-day marathon poker tournament that ended on Tuesday in Philadelphia.

While machines have beaten humans over the past two decade in chess, checkers and, most recently, in the ancient game of Go, Libratus' victory is significant because poker is an imperfect information game. It is similar to the real world, where not all problems are laid out, and the difficulty in figuring out human behavior was one of the main reasons why poker was considered immune to machines.