There are many computational problems in which it’s difficult to find a solution, but relatively easy to verify a solution.
Before looking at the list of items, we have no idea where the marked item is. Therefore, any guess of its location is as good as any other, which can be expressed in terms of a
uniform superposition
How many times do we need to apply the rotation? It turns out that roughly √NN\sqrt{N} rotations suffice.
