Quantum separability of thermal spin one boson systems

Using the temperature Green's function approach we investigate entanglement between two non-interacting spin 1 bosons in thermal equilibrium. We show that, contrary to the fermion case, the entanglement is absent in the spin density matrix. Separability is demonstrated using the Peres–Horodecki criterion for massless particles such as photons in black body radiation. For massive particles, we show that the density matrix can be decomposed with separable states.