Another month, another rationality quotes thread. The rules are:
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Scott Aaronson on why quantum computers don't speed up computations by parallelism, a popular misconception.
The misconception isn't exactly that quantum computers speed up computations by parallelism. They kinda do. The trouble is that what they do isn't anything so simple as "try all the possibilities and report on whichever one works" -- and the real difference between that and what they can actually do is in the reporting rather than the trying.
Of course that means that useful quantum algorithms don't look like "try all the possibilities", but they can still be viewed as working by parallelism. For instance, Grover's search algorithm start... (read more)