Under what circumstances could particles become entangled without our intervention? How frequent would that have happened in the various stages of cosmic expansion?
Is it possible that particles may have been entangled in early cosmic history and remain so today?
If the answer to the third question is 'Yes', would not the search for the modulation of these early entangled particles be of tremendous value?
Consider that particles were very close together in early cosmic development. If those entangled particles are now hundreds of light years apart, and have other particles that are also entangled (group entanglement), would those particles not be a means to detect the communications/modulations of other species who have also discovered the entanglement phenomenon and are subsequently 'listening across the cosmos' for those modulations as well?