# Short question about probability amplitudes

1. May 8, 2012

When one says the probability amplitude for a quantity when it has probability P, which one does one take, the a+bi or the a-bi?

2. May 8, 2012

### facenian

I don't understand your question, perhaps you should try with an example

3. May 8, 2012

### mathman

I am not fully familiar with the subject, but it is either |a+ib| or a2 + b2

4. May 8, 2012

### Ken G

I think the problem is, you are asking the question backward. Many probability amplitudes give the same probability, so you can infer the probability from the amplitude, but not the other way around. Thus your question is like asking how old are all the people who have a May 1 birthday.

5. May 8, 2012