Quantum Tic Tac Toe for Two on One Device

What is quantum tic tac toe?

Quantum tic tac toe is a 3 by 3 board where one move marks two squares. X starts, and a classical line of three wins. This page plays a simplified variant, and it does not use Goff's half-point scoring.

You play quantum tic tac toe on this page by passing one phone. Quantum tic-tac-toe play and entanglement tic tac toe name that same match.

Quantum noughts and crosses is the older name for the marks. The page shows the link between the two squares until someone collapses the cycle.

Why does one phone matter?

One phone matters because the collapse has to be chosen in the room. Passing one phone across a table when the rules are easy to argue is the ordinary case.

Playing a full match without creating an account keeps the score in the open page, and nothing is saved. A coin flip can still decide who is X.

Tic tac toe is the classical board, where one tap is one mark and it stays.

How does a move work?

A move marks two different squares with the same number. The board draws a line between them.

For example, X taps the top left and the top middle. Those squares read X1. O taps the top middle and the top right. Those squares read O2, and the top middle now shows both letters. X taps the top right and the top left. That third mark closes a cycle.

The banner then asks O to choose the collapse. Both ways to settle the cycle are listed before the choice.

How does a cycle collapse?

A cycle collapses into one classical mark on each square it touches. The player who did not close the cycle picks which of the two resolutions lands.

• Spooky marks may share a square
• A classical square takes no further mark
• Only a classical line of three wins
• A board with no pair of open squares left, and no line, is a draw

For example, the cycle above can leave X on the top left, O on the top middle, and X on the top right. The other resolution swaps which end each mark keeps.

For example, if one collapse gives both players a classical line, the earlier line takes the point. The later line does not take a half point, unlike Goff's original scoring. The score stays a whole number.

How is this different from classical tic tac toe?

A classical mark is a single X or O that has already collapsed. A spooky line is still entangled, so it does not win.

Unlike the classical board, you do not choose your own collapse. Seeing which squares a move linked before anyone calls a win is the point of the lines on the grid.

The page does not teach the mathematics behind the name. This board lives in the games category.

What does the note refuse?

The note refuses a mark that the rules do not allow, and the turn stays put. A square that already collapsed says it already has a classical mark.

Undo puts the links back when the last ply was a collapse. Taking back a collapse that the other player wants to reconsider restores both choices.

Avoid refreshing mid-match and expecting the score to still be there. However, rematch keeps that tally, starts from an empty board, and the other player moves first.