Hacker News Reader

Those approaches are increasingly well-studied and a lot of them (Grover's algorithm, anyone?) look an awful lot like magic.

(For people who don't want to look that up, Grover's algorithm does searches on unsorted databases in root-n time, that is, in fewer operations than would be required to inspect every element of the database.)

View on HN

Grover's algorithm does indeed look rather like magic, but even better is the geometrical proof - WP's description looks good at a quick skim. In my (fairly limited) experience, this sort of geometrical thinking is the best way to understand quantum algorithms intuitively.

Although Grover's algorithm is extremely impressive...it's a probabilistic algorithm, which means that the result is not guaranteed, but very likely. And the likelihood can be increased by running the algorithm more than once.

The likelihood increases exponentially because each time you run the algorithm it's independent of the previous times. Even if it's only 75% sure, you only need to run it a few dozen times before it's more likely for there to be a hardware fault in your display giving you the wrong answer.

Reply on news.ycombinator.com