A quantum strategy could solve unsolvable problems

Imagine, for example, that you have a friend who claims to have deduced how to tell the difference between Pepsi and Coke, even though you can’t distinguish between the two. To confirm this claim, you — the verifier — might prepare a cup of either Pepsi or Coke and query your friend — the prover — on which one it is. If your friend consistently gives the right answer to such questions, you’d be convinced that the cola-identification quandary had been solved.