How Can We Manipulate 8 Quantum Combinations with Qubit Computing?

[Edward Wij]

I'd like an actual example of qbits operations. Supposed we have 3 electrons in superposition of spin up and spin down.. then we have total of 2^3 or 8 combinations of information. Can you give an example of how to manipulate the 8 combinations using classical computer and quantum computer? I know the latter can produce all 8 combinations at same time. But if we collapse it there is only one outcome.

Just for sake of illustration. Supposed you could access all the observables or eigenvalues at the same time in the 8 different branches of Everette universal wavefunction. How do you take advantage of the parallel computing of all branches versus just one branch.. please give examples of the 3 electrons with spin up and spin down producing 8 combinations in superposition. I'd just like an idea of what qbit computing by actual example of them. Thanks a lot.

 

[georgir]

I'll start by saying I understand approximately zero of all of this. But while waiting for someone else to step in, I can still give you some links you can try to bang your head against like I did. Maybe the results will be better in your case.

About what operations you can do with quantum bits:
http://en.wikipedia.org/wiki/Quantum_gate
Notice that even for a single qbit there are a ton of possible "gates" that make my brain melt. If you endure till the end, the last two examples are for a set of three qbits (the 8x8 matrices).

About how this is all used for computations in practice:
An explanation of Shor's factoring algorithm: http://www.scottaaronson.com/blog/?p=208
A course on the subject by the same guy: http://www.scottaaronson.com/democritus/default.html

As a short summary I'll just say that the idea that "quantum computing let's you try all the variants in parallel due to superposition" is a misconception, and is not how things actually work.