Communication complexity is an area of classical computer science which studies how much communication is necessary to solve various distributed computational problems. Quantum information processing can be used to reduce the amount of communication required to carry out some distributed problems. We speak of pseudo-telepathy when it is able to completely eliminate the need for communication. Since it is generally very hard to perfectly implement a quantum winning strategy for a pseudo-telepathy game, quantum players are almost certain to make errors even though they use a winning strategy. After introducing a model for pseudo-telepathy games, we investigate the impact of erroneously performed unitary transformations on the quantum winning strategy for the Mermin-GHZ game. The question of how strong the unitary noise can be so that quantum players would still be better than classical ones is also dealt with.
A pseudo-telepathy game is a game for two or more players for which there is no classical winning strategy, but there is a winning strategy based on sharing quantum entanglement by the players. Since it is generally very hard to perfectly implement a quantum winning strategy for a pseudo-telepathy game, quantum players are almost certain to make errors even though they use a winning strategy. After introducing a model for pseudo-telepathy games, we investigate the impact of several basic noisy quantum channels on the quantum winning strategy for the Mermin-GHZ game. The question of how strong the noise can be so that quantum players would still be better than classical ones is also dealt with.
In 1990, Mermin presented a n player game that is won with certainty using n spin-1/2 particles in a GHZ state whilst no classical strategy (or local theory) can win with probability higher than
1/2+2⌈n/2⌉1 (which is larger than 1/2). This article first introduces a class of arithmetic games containing Mermin's and gives a quantum algorithm based on a generalized n party GHZ state that wins those games with certainty. It is then proved for a subclass of those games where each player is given a single bit of input that no classical strategy can win with a probability that is asymptotically larger than 1.6 times the inverse of the square root of n, thus giving a new and stronger Bell inequality.