Sir Peter Knight, The Physicist Who Helped Build Britain’s Quantum Programme

He taught British quantum physics how to cost itself honestly, which is why a government eventually handed him the pen. In 1996, two years after Peter Shor showed that a quantum computer could break the encryption underpinning the internet, and while the field was still enjoying the discovery, two theorists at Imperial College London sat down and worked out how long it would actually take. Martin Plenio and Peter Knight published the answer in Physical Review A under a title that gives away the mood, Realistic lower bounds for the factorization time of large numbers on a quantum computer, and it consisted of arithmetic rather than enthusiasm. Thirty years later Knight chairs the Strategic Advisory Board of the United Kingdom’s National Quantum Technologies Programme, the body through which scientific judgement reaches the departments that hold the money, and the money is now considerable. The programme’s own governance pages describe the board as advising on the implementation of a ten-year National Quantum Strategy worth £2.5 billion. Those two facts are the same fact. A government deciding how much to spend on an emerging technology needs somebody who can tell it what the technology will cost before it works, and that is…