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I understand in plain terms superposition and entanglement, but I'm very unclear how either of these could work as a means to increase computation power.

A helpful metaphor is that of the maze. A normal computer must work through every path of the maze to find the exit. If it takes a wrong turn, it must start over. This is time-consuming. On the other hand, a quantum computer can work through every path simultaneously. Obviously, this is more efficient.

But that metaphor doesn't explain how superposition makes this possible because it doesn't describe how a quantum computer would execute the calculation/process.

So what I'm looking for is an explanation of that, how does a quantum computer execute a process by leveraging superposition?

That qubits collapse under observation seems to make the whole thing useless.

Let's say I have a dictionary of possible passwords. One password is correct. I can create a function that loops through every word in the dictionary and attempts to use it as the password.

The password is stored in a variable called "temp". In a quantum world, if "temp" was made of qubits, it could have a multitude of values at once, drastically reducing the number of times we would need to run the password test.

But in order for the test to execute, wouldn't we need to observe the value of "temp" and therefore collapse the potential states?

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    $\begingroup$ Like really? Fortunately the body of your question makes up for the title. $\endgroup$
    – my2cts
    Oct 7, 2021 at 21:39
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    $\begingroup$ quantumcomputing.stackexchange.com $\endgroup$ Oct 7, 2021 at 21:45
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    $\begingroup$ The "metaphor" you suggest is just plain wrong, so it's no surprise that it doesn't help your intuition at all. Quoting the header on Scott Aaronson's blog "If you take nothing else from this blog: quantum computers won't solve hard problems instantly by just trying all solutions in parallel." $\endgroup$
    – d_b
    Oct 7, 2021 at 22:13
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    $\begingroup$ A starting point to understand the power of quantum computation is the Deutsch-Jozsa algorithm. This solves a problem that classicaly takes $2^{n-1}+1$ queries to a black box function with only $1$ query to the quantum equivalent of said black box function. $\endgroup$
    – epelaez
    Oct 7, 2021 at 22:18
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    $\begingroup$ Another starting point is to understand Shor's factorization algorithm. $\endgroup$
    – WillO
    Oct 7, 2021 at 23:53

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