I try to understand the 'Quantum Approximate Optimization Algorithm' (QAOA) by Farhi et al. - arXiv:1411.4028.
I understand that the solution is hidden in the unitaries, but I do not understand how to choose the angles and how to optimize them. If I start with a circuit depth of $m=1$, I only have two angles. How do I choose them?
After choosing them I create the state by using the Quantum Computer - so using the unitaries and subsequently measuring the expectation value of the first qubit. Doing the same, measuring the second qubit... and so on. Afterwards I sum everything together and I have a got a result for the energy of the whole system, right? The paper says "Repeat with the same angles" - why?
Now, the algorithm says, one should optimize the angles - but how? Everything we have at this point, is a state and a corresponding energy.