(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Hi

I have read a paper, where they want to find the average number of photons in a cavity. They have an expression for [itex]\langle{\hat a}\rangle[/itex], and then they use

[tex]

\langle{\hat a}\rangle^* = \langle{\hat a^\dagger}\rangle

[/tex]

to find [itex]\langle{\hat a^\dagger \hat a}\rangle[/itex]. I agree with the above relation, however what I don't agree with is the following equality

[tex]

\langle{\hat a^\dagger \hat a}\rangle = \langle{\hat a}\rangle^*\langle{\hat a}\rangle

[/tex]

Am I right? I mean, one can't just factorize an expectation value like that.

Best,

Niles.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: QM: Product expectation value

**Physics Forums | Science Articles, Homework Help, Discussion**