Quantum tic-tac-toe is based on the classic children’s game of tic-tac-toe. International readers may be more familiar with the label Naughts & Crosses.

It generalizes tic-tac-toe by introducing superposition. On each move, two squares are marked, rather than just one. In allusion to Einstein’s quip about spooky action-at-a-distance, the pair of marks are called, spooky marks. A move is not in both squares, nor neither, but rather half in one square, half in the other - think of it as the square root of a move. This produces a game which metaphoricaly acts as a toy universe for one aspect of quantum systems - the phenomenon of superposition. Each move is literally in two places at once, a ‘super’-position.

As a toy universe quantum tic-tac-toe achieves two conceptual gains; it offers an intuitive interpetation of superposition and more telling, it reveals an objective measurement mechanism, one based on self-reference.

It is a portent of the utility of the core epiphanies of this quest; games and self-reference.

Last updated: 2026-02-23