add more doc on similarity and diff between QAOA + VQE
@@ -98,10 +98,15 @@ Quantum Approximate Optimization Algorithm (QAOA)
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`QAOA <https://arxiv.org/abs/1411.4028>`__ is an well-known algorithm for finding approximate solutions to
-combinatorial optimization problems. Similar to VQE, it also uses the variational approach
-for the classical optimization part. But QAOA uses its own fine-tuned variational form comprised of
-parameterized global ``X`` rotations as well as the problem hamiltonian, with a single parameter
-``p`` dictating the depth of the variational form, and thus affecting the approximation quality.
+combinatorial optimization problems.
+Our QAOA implementation directly uses VQE for its general hybrid optimization structure.
+But unlike VQE who can be configured with arbitrary variational forms,
+QAOA uses its own fine-tuned variational form,
+which is comprised of ``p`` parameterized global ``X`` rotations,
+as well as another ``p`` parameterized problem hamiltonian themselves.
+Therefore, rather than needing to have a variational form specified like VQE,
+QAOA is configured mainly by a single integer parameter ``p``,
+which dictates the depth of the variational form, and thus affecting the approximation quality.
Similar to VQE, an `optimizer <./optimizers.html>`__ may also be specified.
Additionally, QAOA can be configured with the following parameters:
