In this superbly insightful, one-stop guide WIRED journalist Amit Katwala tells you everything you need to know about the next computer revolution. He explains the highly complex science that lies behind it. He describes the competing efforts of the likes of Google, Microsoft and Chinese companies Tencent and Alibaba to create a viable quantum computer, and the different routes they have taken to meet the immense technical challenges involved. He considers the technology's potential application in spheres as diverse as medicine, cyber security and clean energy. And he addresses the fundamental question: how close are we to seeing quantum computers become a widespread reality.