You can't directly compare optical and electrical compute through looking at the difference in feature densities. Optical compute will most likely take the form of analog waveforms that contain many bits of information, whereas electronics for computing is inherently binary.
I'm afraid that's not even remotely true. Just two counterexamples:
- MLC flash storage devices use multiple levels to store/retrieve bits [1],
- Lots of control systems are implemented with analog PIDs [2]. A trivial example is a jellybean voltage regulator that computes the adjustments needed to maintain a stable output voltage independent of the load.
