What's closer to practical application these days, photonic/optical computing or quantum computing (silicon or not)?

Photonic computing has a lot of practical applications for signal transfer already.

Basically anytime we send a signal across a large fiber optic cable we need to convert signal from light back to electricity and that requires some level of photonic computing. Its used at scale today. https://www.ebsco.com/research-starters/science/photonics

However I suspect that you mean photonic computing where a computer on chip device uses photons instead of electrons to communicate. In which case, as far as I know is still research phase.

Thank you, I didn't know that. and you were right, I meant photons instead of electrons being used at the processor logic-gate level.

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