In the quantum chess computer game created by computer science student Alice Wismath (right), a piece that should be a knight could simultaneously also be a queen, a pawn or something else. Wimath based the game on an idea proposed by computer science professor Selim Akl, left. (Kristyn Wallace/Queen’s University)
The unpredictable nature of quantum physics has been mimicked by Queen’s University computer scientists to invent a new version of chess.
In the quantum chess computer game created by undergraduate computer science student Alice Wismath, a piece that should be a knight could simultaneously also be a queen, a pawn or something else. The player doesn’t know what the second state might be or which of the two states the piece will choose when it is moved.
“It was very weird,” said Ernesto Posse, a Queen’s postdoctoral researcher who took part in a recent “quantum chess” tournament at the university in Kingston, Ont. “You only know what a piece really is once you touch the piece. Basically, planning ahead is impossible.”
According to quantum physics, very small particles behave according to principles that give them characteristics very different from the behaviour of larger objects. Here are a few properties of those quantum objects:
Quantum superposition: A quantum object may exist in multiple states at the same time.
Wave function collapse: An observer’s interaction with a quantum object in a superposition of states, such as an attempt to measure its position or momentum, will make it “collapse” into a single state.
Quantum entanglement: Two or more quantum objects may be linked so that any change to one is immediately experienced by another, no matter how far apart they are from one another.
Wismath wrote the game based on ideas proposed by Selim Akl, a computer science professor at Queen’s, in a paper that will be published in September in a special issue of Parallel Processing Letters. Akl is editor-in-chief of the journal, but not that special issue.
Computers can search all possible outcomes of all possible moves in conventional chess and beat even top human players, so Akl wanted to make the computation more difficult.
He decided to have the pieces mimic the behaviour of very small particles such as atoms and electrons, which follow the laws of quantum mechanics. According to the principle of superposition in quantum physics, such particles can simultaneously be in multiple states at once, but collapse into a single state when an attempt is made to measure their position, momentum or some other aspect.