For a long time my standard answer to the question ‘how long will it be before the first universal quantum computer is built?’ was ‘several decades at least’. In fact, I have been saying this for almost exactly two decades … and now I am pleased to report that recent theoretical advances have caused me to conclude that we are within sight of that goal. It may well be achieved within the next decade.
The main discovery that has made the difference is cluster quantum computation, which is a marvellous new way of structuring quantum computations which makes them far easier to implement physically.