Quantum coherence of photons at cosmological distances

Understand

We identify potential sources of decoherence for $U(1)$ gauge bosons from a cosmological standpoint.

• Besides interactions with different species in the cosmological medium, we also consider effects due to the expansion of the Universe, which can produce particles (especially scalars) than can potentially interact with the photon in a quantum state.
• We look in particular at the case of axion-like particles and their predicted decay channels in our analysis.
• These interactions are shown to have a negligible effect as far as decoherence goes.