The physics of optical computing
This Perspective article provides a systematic explanation of why and how optics might be able to give speed or energy-efficiency benefits over electronics for computing, enumerating 11 features of optics that can be harnessed when designing an optical computer.
Abstract
There has been a resurgence of interest in optical computing since the early 2010s, both in academia and in industry, with much of the excitement centred around special-purpose optical computers for neural-network processing. Optical computing has been a topic of periodic study since the 1960s, including for neural networks in the 1980s and early 1990s, and a wide variety of optical-computing schemes and architectures have been proposed. In this Perspective article, we provide a systematic explanation of why and how optics might be able to give speed or energy-efficiency benefits over electronics for computing, enumerating 11 features of optics that can be harnessed when designing an optical computer. One often-mentioned motivation for optical computing — that the speed of light is fast — is emphatically not a key differentiating physical property of optics for computing; understanding where an advantage could come from is more subtle. We discuss how gaining an advantage over state-of-the-art electronic processors will likely only be achievable by careful design that harnesses more than 1 of the 11 features, while avoiding a number of pitfalls that we describe. Optical computing has the potential to be faster and more energy-efficient than conventional digital-electronic computing for certain applications. This Perspective article surveys the differences between optics and electronics that could be exploited, and explores the physics and engineering challenges in realizing useful optical computers.