  The Quantum Alternating Operator Ansatz (QAOA) and its predecessor, the
Quantum Approximate Optimization Algorithm, are one of the most widely used
quantum algorithms for solving combinatorial optimization problems. However, as
there is yet no rigorous proof of convergence for the QAOA, we provide one in
this paper. The proof involves retracing the connection between the Quantum
Adiabatic Algorithm and the QAOA, and naturally suggests a refined definition
of the `phase separator' and `mixer' keywords.
