This Computer Uses Light--Not Electricity--To Train AI Algorithms

William Andregg ushers me into the cluttered workshop of his startup Fathom Computing and gently lifts the lid from a bulky black box. Inside, green light glows faintly from a collection of lenses, brackets, and cables that resemble an exploded telescope. It's a prototype computer that processes data using light, not electricity, and it's learning to recognize handwritten digits. In other experiments the device learned to generate sentences in text. Right now, this embryonic optical computer is good, not great: on its best run it read 90 percent of scrawled numbers correctly.