Bose-Einstein condensates coherence

[Bone Rasta]

Hello forum! I'm studying classical and quantum coherence and there's some bug in particular I can't solve on my own, nor I could find anywhere.
I've read that a Bose-Einstein condensate is a coherent state but it seems to me inconsistent with the definition of coherence given by Glauber. In fact, he showed that a thermal source (which follows a B-E distribution), is not second order coherent because of the correlation among particles. Am I missing something?

 

[nbryan5]

Yes, you are missing something! Bose-Einstein condensates (BECs) are indeed a special type of coherent state. However, they are not the same as a thermal source, which follows a Bose-Einstein distribution. The coherence of a BEC is due to its extremely low temperature and the fact that all particles in the system occupy the same quantum state. This means that the particles in a BEC are perfectly correlated, and this is what gives rise to its second order coherence.