The optical stuff is still research territory and too early to be comparable to the current digital silicon. Lots of open questions about how to implement multi

The optical stuff is still research territory and too early to be comparable to the current digital silicon. Lots of open questions about how to implement multiplication, implement activation functions, where to store weights, how to move data in and out, manufacturability of all of this, etc. Basically it's all questions. To get some intuition about the promise imagine being able to implement the weights of a layer (fully connected layer is essentially vector matrix multiplication) as a 2D hologram and the compute as pushing an image from an OLED display through to an image sensor. Multiplication as attenuation in the hologram, summation is just the accumulation of charge on the sensor side. Everything happens all at once and the number of photons required is potentially very small. An actual working implementation would be both more clever and more practical. The potential to do every multiply in parallel for almost no energy is so attractive that I expect people to chip away at this problem for the foreseeable future.