Introduction Is there entanglement of black body radiation such as cosmic background radiation or black hole radiation? Entanglement of non-interacting Fermi gases Creation of entanglement by interacting with thermal bath

Green’s function HF approx. where , Two particle density matrix Finite temperature two body Green’s function HF approx. One particle density matrix and One body Green’s function where ,

If and then where In basis Generalized Werner State where & Separability criterion=PPT= always satisfied since No entanglement in two-spin density matrix of non-interacting thermal boson!

Classical correlation for BB radiation Fidelity Temperature dependency where , , Classical correlation

Classical correlation

Aspect type experiment a,a’ b,b’ Bell-CHSH inequality

Fermion Case

Conclusion No two-spin entanglement in non-interacting thermal boson system Useful for determining the character of light sources Need to study interacting case and system with phase transition