By combining quantum computation and quantum interrogation, scientists at the University of Illinois at Urbana-Champaign have found an exotic way of determining an answer to an algorithm – without ever running the algorithm.
Utilizing two coupled optical interferometers, nested within a third, Kwiat's team succeeded in counterfactually searching a four-element database using Grover's quantum search algorithm. "By placing our photon in a quantum superposition of running and not running the search algorithm, we obtained information about the answer even when the photon did not run the search algorithm," said graduate student Onur Hosten, lead author of the Nature paper. "We also showed theoretically how to obtain the answer without ever running the algorithm, by using a 'chained Zeno' effect."
This is why I hate quantum mechanics. Wave-particle duality, fine. Uncertainty principle, fine. Superposition, fine. I can even cope with there being no hidden variables and the potential for "spooky action at a distance". But eventually, my head just explodes...
J.B.S. Haldane was right: "Reality is not only stranger than we imagine, it is stranger than we can imagine".