# Derivation of Sudarshan-Glauber P function

1. Jun 4, 2016

### Muthumanimaran

1. The problem statement, all variables and given/known data
It is not a problem, But I am doing a coursework on Quantum Optics on my own. The following derivation is for P-function in Quantum optics from the book Quantum Optics by Marlan O.Scully and M. Suhail Zubairy. I attached the Image of the derivation with this Question.

2. Relevant equations
Relevant Equations are given in the Image

3. The attempt at a solution
I expanded the trace in the (3.1.11) in |α> basis. But I am unable to get (3.1.13).

File size:
38.3 KB
Views:
78
2. Jun 4, 2016

### nrqed

They are just saying that (by definition),

$$\int d^2 \alpha ~~\delta(a- \alpha) \delta(a^\dagger - \alpha^*) f(\alpha) f(\alpha^*) = f(a) f(a^\dagger)$$

3. Jun 4, 2016

### Muthumanimaran

Yeah I absolutely understand that, but I don't know how to expand f(a)f(a†). Can you help me with this?

4. Jun 4, 2016

### nrqed

Ah, but then 3.1.13 follows directly from 3.1.11 with the choice $f(a) = a^m$ and $f(a^\dagger) = (a^\dagger)^n$. That's all there is to it. I am not sure what the question is, then.

5. Jun 5, 2016

### Muthumanimaran

Oh yes, I confused myself a bit. Now I got. Its pretty straightforward. Thank you.