Quantum Computing since Democritus

by Scott Aaronson

the outcome of this measurement could be predicted almost with certainty given this state, you can prove, because of that, that you aren't getting a lot of information, and so the state is only slightly disturbed by the measurement. This is just a general fact about quantum measurements. If you could predict the outcome with certainty, then the state wouldn't be disturbed at all by the measurement.6