From Nature, a more descriptive article on the quantum computer that can solve problems before even running:
A quantum computer is very different from a traditional desktop computer. It uses the laws of quantum mechanics to perform many calculations at once where a conventional computer could do them only one at a time. This drastically cuts the time a quantum computer takes to find the answer.
This is made possible by the fact that quantum objects, such as individual atoms or photons of light, can be placed in ‘superposition’ states, mixtures of states that are mutually exclusive in everyday objects. A quantum switch, for example, could be simultaneously on and off.
That’s the key to quantum computation, because it means that a quantum computer can be placed in a superposition of states where it is running and not running. This leaves an imprint of the ‘running’ state on the history of the ‘not running’ state, such that one can look at the latter and determine something about the former.
“Some people like to think of this as two different universes”, explains computer scientist Richard Josza of Bristol University in England. In one universe the computer runs, while in a parallel universe it doesn’t.
One might say then that the computer does actually run, but in a ‘parallel universe’. “So you wouldn’t be charged for the cost of running it,” says Josza.