Does the paper propose building these devices in free space? I got the sense this was all intended to be produced lithographically with waveguides, so alignment wouldn't be a problem.
The title is wrong about it being an integrated design. Here's an excerpt from the paper abstract:
"This paper presents a new type of photonic accelerator based on coherent detection that is scalable to large (N≳106) networks and can be operated at high (gigahertz) speeds and very low (subattojoule) energies per multiply and accumulate (MAC), using the massive spatial multiplexing enabled by standard free-space optical components"
