Comment by tim333
2 days ago
Thanks for the reply. I've always been a bit puzzled from my limited knowledge of quantum mechanics as to how they are supposed to work. I mean you make a measurement on a quantum system and sure the probability amplitude is the result of adding up all sorts of possible paths but you still only get the one measurement out which I'm not sure how that's supposed to tell you much. All a bit beyond me.
Does https://scottaaronson.blog/?p=208 help?
(Also, the factoring-21 result is from 2012, and may have been surpassed since then depending on how you count. Recent quantum-computing research has focused less on factoring numbers and more on problems like random circuit sampling where it's easier to get meaningful results with the noisy intermediate-scale machines we have today. Factoring is hard mode because you have to get it exactly right or else it's no good at all.)
Helps a bit thanks. I guess it's a bit like in x ray crystal diffraction you get light and dark patches depending on how the photon paths interacting with trillions of atoms add up, with a quantum computer you'd get light or dark outputs depending on how the amplitudes of trillions of calculations add up?
you typically have to sample multiple times until you can build up the distribution that you can convert to a solution to your problem.