Lets say we have a fully working quantum computer. I give it a problem to solve and measure how long it takes to solve it. I repeat the process. Would it take the exact same time to solve the same problem?
I have read that a quantum computer's solution process could be seen as all the potential answers are already calculated but to get it out of an entangled state without changing the result, you would use Grover's algorithm that reduces the answer set. You then repeat Grover's algorithm to keep on reducing the answer set. Now you could repeat Grover's algorithm to get a single answer or just start up classical computing to test answers once the answer set is small enough.
This could possibly mean that the same problem could have a different answer set on first iteration of Grover's algorithm which could cascade on how many times it needs to run to get to a reasonably small answer set to test with classical computing.
Did I misunderstand something or is it reasonable that same problem could have varying calculation time on same hardware?