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This page is written by the game's inventor, Theodoros Papadopoulos.

Entangled chess

Entangled Chess is a chess variant played on a standard 8x8 chess board with all pieces and pawns having the same characteristics of orthodox chess. Nevertheless, the two kings find themselves in a “quantum” state that keeps them entangled. This variant is inspired by the phenomenon of quantum entanglement initially investigated by A. Einstein, B. Podolsky and N. Rosen [1] as well as E. Schrödinger [2], formulating the early days of the so-called EPR paradox.

[1] A. Einstein, B. Podolsky and N. Rosen, Phys. Rev. 47, 777 (1935).

[2] E. Schrödinger, Math. Proc. Cambridge Philos. Soc. 32, 446 (1936).


The board setup is identical to that of orthodox chess.


Pawns and pieces of entangled chess are the same with those of orthodox chess and have the same initial placement on the chessboard.


Pawns and pieces of entangled chess move in accord with the rules of orthodox chess with the only difference that the white and black kings are entangled. This means that when one king moves, then the other must do the same move simultaneously on his side of the board. Nevertheless, if the latter cannot occupy that square, then this move is inaccessible to the former. The interesting complication of this rule is that both players can manipulate the opposite king as long as both kings occupy the same square (or “quantum” state) on their side of the board. At any time, the positions of the two kings obey point reflection symmetry with the symmetry “point” being the interface between squares e4 and e5.

Example visualised on the Figure below: Black bishop moves from f8 to b4. The white king is checkmated as the two squares that he could move to (e2 and f1) are inaccessible due to the black entangled king being unable to move to squares e7 and d8. Black win!

HTML picture of the first game of entangled chess
Figure: The white king is checkmated! Image taken from gnome-chess as a print-screen after the first game of entangled chess was completed on Sept. 14, 2015.


In this chess variation, the white and black kings are entangled throughout the game until one is checkmated and quantum chess coherence is destroyed! Players could decide if they would like to include more entangled pieces into the game, for example a white and a black knight could also be entangled.

In Greek, entangled chess is called «εναγκαλισμένο σκάκι», pronounced as "enɑgɑlɪsmeno skɑkɪ".

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By Theodoros Papadopoulos.
Web page created: 2015-09-20. Web page last updated: 2015-09-20