"Single-chip photonic deep neural network with forward-only training" (2024) <a href="https://www.nature.com/articles/s41566-024-01567-z" rel="nofollow">https://www.nature.com/articles/s41566-024-01567-z</a> :<p>> <i>Here we realize such a system in a scalable photonic integrated circuit that monolithically integrates multiple coherent optical processor units for matrix algebra and nonlinear activation functions into a single chip. We experimentally demonstrate this fully integrated coherent optical neural network architecture for a deep neural network with six neurons and three layers that optically computes both linear and nonlinear functions</i> [...]<p>> <i>This work lends experimental evidence to theoretical proposals for in situ training, enabling orders of magnitude improvements in the throughput of training data. Moreover, the fully integrated coherent optical neural network opens the path to inference at nanosecond latency and</i> femtojoule per operation energy efficiency.