Top players have spent lifetimes mastering the subtle nuances of chess, but when a quantum physics twist is added to the age-old classic, it's anybody's games.


A quantum object can exist in more than one state. When you attempt to interact with it, the wave function collapses and the object settles into a single state. This is the theory applied to Quantum Chess, a new twist on the classic game created by Queen's University undergraduate computer science student Alice Wismath.

Wismath wrote the game based on ideas from computer science professor Selim Akl at Queens. Akl wanted to make the process of predicting chess moves using computers more difficult. In order to achieve this, he decided to have the pieces mimic the way particles like electrons and atoms behave according to the laws of quantum mechanics.


Any given piece (aside from the king) has multiple quantum states. A pawn might also be a queen; a knight a bishop, and so on. The player doesn't know how the piece is going to move until he or she touches it, which forces it to settle into one state.

"I thought of a game that provides the same kind of unpredictability to both players," Akl said. "The computer cannot possibly search all the possibilities because we can show there are an uncountable number of them."

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The twist makes it nearly impossible to plan ahead in a game. Wismath, who programmed the computer to attempt to predict a player's movements had to limit its calculations to the next possible move and the human response after it. Normal computer chess calculations rely on an outcome tree, scoring the potential moves according to the pieces involved. When you don't know what piece is going to pop up, it becomes extremely tough to calculate scores.

Ernesto Posse, a Queen's postdoctoral researcher and longtime chess player won a recent Quantum Chess tournament held at Queens University in Kingston, Ontario, but he doesn't attribute the win to skill.

Posse, who has been playing chess for 15 years, said the new game doesn't much resemble the classic contest he likes for its tactics, strategy and history: "I would say it's 'chess-inspired.'" He was one of the winners in the tournament , but credits luck.

Other players, like Chris Perez, a master's student in computer science, say there is still room for strategy. He suggests using your memory to figure out which pieces on the board have yet to be revealed, planning out your moves on the chance that a weak piece might be hiding a much stronger one.

"Adding an element of chance makes things more fun."

Want to try it out for yourself? Play Quantum Chess here.

Quantum physics adds twist to chess [CBC News]