[quantadev]

I didn't say sending single photons at a time is a viable communications mechanism. I said a photon will travel indefinitely, without losing any energy, until it interacts with something.

Interestingly, if you send out a single photon from a radio antenna not even the universe itself will have 'determined' which direction it even went until it DOES interact, because there would be a Quantum Mechanical superposition/indeterminacy similar to the famous slit-experiment, if you were dealing with one photon at a time.

So even the thought experiment itself is complex due to wave/particle duality.