I was considering buying a new desktop computer, and I thought I had found the ideal model. That is, until I noticed that one little thing was missing—the ­activity light for the hard drive. The manufacturer probably saved a few cents by ­leaving it out, but that little light was of some psychological ­importance to me. How could I possibly buy a computer that was just going to sit there and not give me any indication that it was working?

A very long time ago, not long after the dinosaurs went extinct, I was ­working on modem design. At the Bell System, we had designed modems the way they were supposed to be—big, heavy clunkers with a telephone handset and an embedded rotary dial. They were just what the users needed to connect to their time-shared mainframes. But one day, a competitor came out with a small modem that had an array of LED lamps on the front panel, indicating control signals like clear-to-send as well as data activity. ”What user could possibly care about such things?” we joked among ourselves.

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The Future of Deep Learning Is Photonic

Computing with light could slash the energy needs of neural networks

10 min read
Image of a computer rendering.

This computer rendering depicts the pattern on a photonic chip that the author and his colleagues have devised for performing neural-network calculations using light.

Alexander Sludds

Think of the many tasks to which computers are being applied that in the not-so-distant past required human intuition. Computers routinely identify objects in images, transcribe speech, translate between languages, diagnose medical conditions, play complex games, and drive cars.

The technique that has empowered these stunning developments is called deep learning, a term that refers to mathematical models known as artificial neural networks. Deep learning is a subfield of machine learning, a branch of computer science based on fitting complex models to data.

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