I actually think we should be revisiting PMT photomultipler tube construction, and electron-"optical" matrix multiplication.
The annoying part of optical matrix multiplication is the conversion from electronic to optic and back.
Why not use electron-optics for matrix multiplication and use dynodes for amplification.
While an intriguing concept, that doesn't sound like it could scale to the amount of "cores" needed to do the work. Or am I missing something?