pre comments on Request For Article: Many-Worlds Quantum Computing - Less Wrong
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Comments (55)
Voted down for being off-topic. Feel free to delve into a deep discussion about the merits of doing this and what should be considered off-topic. Meanwhile, I'll say what I have to say anyway. Feel free to delve into a deep discussion about the merits of doing this as well.
The thing is, quantum mechanics looks like the Copenhagen interpretation. That's why Copenhagen hasn't been falsified. We've barely managed to produce any evidence against it. (I'm not considering its low-ish prior probability to be evidence, of course.) Therefore, if you want to explain an observed phenomenon, it's perfectly valid to explain it in terms of wavefunction collapse.
Note to self: ponder, and write something about, when it makes sense to explain something in terms of a mechanism you don't know exists.
Saying that a quantum algorithm is "simultaneously sampling all possibilities and choosing the best one" has always been, I've found, a strange way of putting it, since it suggests that quantum computing can do a lot more than it actually can. (Quantum superintelligence: simultaneously sample every possible process of reasoning and choose the most interesting one. Unfortunately, you can't actually do that.)
A quantum algorithm such as Grover's algorithm simply works by changing the probability amplitudes (i.e. the heights of the wavefunctions, the things that can interfere constructively and destructively, the things that determine the probability of each outcome) in such a way that the probability of the desired answer is much higher than the probability of any other answer. ("Probability" here is just a specific function of probability amplitude, which happens to be consistent with both quantum evolution and the laws of probability.) When you perform the observation, then, the majority of Bornstuff goes to the world where the answer observed is the desired one.
How does Grover's algorithm work, specifically? Well, there's a plane where one line is the algorithm's starting point, and another line is the correct answer; it uses reflections to rotate the point for a certain amount of time, until it's very close to the correct answer. I dunno. For details, see Wikipedia.
Indeed, misleading and annoyingly common and the kinda thing that's always encouraging my more cosmic hippy friends down blind alleys. I'm hoping to find a better way, it seemed to me that MWI might have done that.
Maybe it doesn't, I'm certainly not an expert, hard for me to tell without being able to read a good one :)
This is better, certainly:
Not far off my assumptions in the original request which is always encouraging.