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).