# Extracting an answer from a quantum computer

1. Jun 30, 2010

### quasi_Phthalo

Suppose you have a quantum apparatus that takes two 3-qubit registers as input, multiplies them, and produces output in a 6-qubit register. If the inputs are initialized as a superposition with equal probability of being each number 000 to 111, then the output will be the superposition of all possible results of the multiplication, right?

Then the output has, for example, a 15/64 chance of being 0, 4/64 of being 12, and 0/64 of being 19, etc., right?

Is there any way to force the output to a specific value, say 35, thereby making each input collapse to a superposition of 5 and 7; then, after measuring them, you find one to be 5 and the other to be 7, effectively having factored 35?

If you CAN extract the desired output, thereby discovering the inputs that yield it, HOW do you do it?

2. Jun 30, 2010

### Eynstone

I don't know if one can 'force' a quantum system to a desired outcome after measurement.