Short question about probability amplitudes

1. May 8, 2012

nomadreid

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

nomadreid

Thanks for the replies.
First, Ken G knew what I was talking about, and his answer makes sense: I gwould guss from his reply that all contexts are "given the probability amplitude A find the probability amplitude B".... ; and none in which you need to find the probability amplitude B given the probability of A. I'll accept that.
Mathman misunderstood my question: I was not asking for the amplitude (which is a2 + b2) but the probability amplitude (which is a+bi such that a2 + b2 = the probability.)
Finally, facenian would like an example of what I am referring to. I am referring to the ψ which you find in quantum mechanics; for example in Schrödinger's equations.

6. May 9, 2012

Ken G

I think you have it now!

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