If you have a laser, you can print an optical neural network using a consumer 3D printer. The present barrier to adoption, as the article describes, is the cost of transitioning from the optical space to the electronic space.
Is it the sunken cost in existing hardware, or developing the rest of the "value chain" to make photonics work, or something else altogether?
The silver lining is that one might need massively less photonic components to get the job done than electronic components due to the former's theoretically magnitudes higher switching frequency. And we might reserve them for graphics and AI at first.
I would love to look into this more. Do you have a reference that would give some instructions on how to give this a go?
Having established that, well, it's not hard to imagine that something that's good at running Fourier transforms is probably good for other situations where you need to run a lot of dot products in parallel. That, in turn, should sound like an awfully familiar problem...
Neural nets, on the other hand, generally require nonlinear operations. As do most computer programs.
So the explanation here is either not complete, or perhaps applies to a very restricted type of neural network only.