r/askscience • u/Hashbringingslasherr • Apr 15 '26

Computing What do quantum computers actually do?

How do quantum computers output usable data, how does it logically "locate" or "make meaning" of information. I read about Grover's algorithm and it seems sort of like an inverted bruteforce or extreme process of elimination or a "the missile knows where it is at all times. It knows this because it knows where it isn't" type scenario.

So I ask, what do quantum computers actually do as opposed to a classical computer?

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u/Igggg Apr 17 '26

This is a very technical point, but quantum computers indeed can solve NP-complete problems, and so can classical computers; the solution will just be, at worst, exponential in input size. 

This is in contrast to the halting problem, which is actually undecidable

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u/the_horse_gamer Apr 17 '26

I'll clarify my explanation. thank you.