Clarification on terminology: PQC vs QNN vs VQC

Codebook
1

I was reading this paper, and it says that PQC, QNN, and VQC are the same (highlighted in the screenshot). But isn’t it that, for instance, QAOA is a VQC but not a QNN?

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2

hi @Afrah! Thanks for your question.
I don’t have enough background knowledge to answer your question, but I’m asking around to get help from others.
I’ll get back to you asap.

3

Dear @Afrah,

Let me come in here, and try to give some more explicit definitions.

  • PQCs (Parametrised Quantum Circuits) and VQCs (Variational Quantum Circuits) are synonyms, and both refer to a quantum computation that depends on parameters that are classically tunable.
  • QNNs (Quantum Neural Networks) refer to the use of PQCs/VQCs in the context of machine learning. They sometimes (but not always, as in generative models) have a data loading step. So they are in some sense PQCs/VQCs with a specific application.
  • QAOA is a specific ansatz or structure of a VQC. It can be used for a QNN as well, if your quantum model for data analysis happens to have that structure.

Hope this helps - it can be a bit of a jungle out there with terminology :slight_smile: