So how do you formulate a useful problem such that a quantum computer will have the amplitudes interfere to create the answer? Can the low number of Q-bit computers available factor small integers, for instance?
This question describes about half the field of quantum computing, so it isn't something I can answer in a post this size.
And yes, a low number of qubits can factor small numbers. https://arxiv.org/abs/1411.6758