Are all particles and photons entangled?

[jjfromspace]

1) are all particles/photons theoretically entangled at birth but we just never or will know? Or is it under specific conditions?
2) how much of the photons that the sun emits entangled particles/photons?

 

[jfizzix]

1) The circumstances of how the particles are created will determine if and how they are entangled at birth. For example, a single excited atom can emit a single photon, and doubly-excited atoms can emit pairs of photons that may be entangled depending on the circumstances.

2) As far as the light that the sun emits, it will mostly be incoherent (unentangled) thermal light, or the same kind of light that all glowing hot bodies emit. The sun is generally more complex than just a glowing ball of hot gas, and if there are some atoms of hydrogen excited to the right energy level they can emit pairs of polarization-entangled photons as they decay back to their ground states.

If you use Boltzmann statistics to figure out the fraction of hydrogen atoms in a doubly excited state in a ball of gas as hot as the surface of the sun, it's still a very very small fraction (about one part in 50 billion). So, even though it's very likely that the sun can and does emit pairs of entangled photons, the fraction of such light compared to the total luminosity of the sun is too small to be measurable.