Google's ultra-private CEO Sundar Pichai is showing me around Googleplex, its California headquarters. A walkway runs along the length of it, passing by a giant dinosaur skeleton, a beach volleyball pitch and dozens of Googlers lunching under the hazy November sun. But it's a laboratory, hidden away at the back of the campus behind some trees, that he is most excited to show me. This is where the invention that Google believes is its secret weapon is being developed. Known as a Tensor