Re: FTL Comms?
"Can you encode data at one ground station and have it immediately received at the other? "
In a word, no. This is sending data via a laser, so the time taken for the data to get from orbit to the ground station will be the same as any other optical communication.
The difference here is that some of the photons sent by the orbital laser are entangled pairs (created in the same event in the laser), and the ground receiver is equipped to be able to identify and read the state of entangled photons.
My (limited) understanding is that if you consider a particular property of a transmitted entangled pair (e.g. polarisation), while in transit both photons will be in a quantum state, neither polarised in one direction or another. However, once they are detected (i.e. 'observed') by hitting a photoreceptor, they reach a non-quantum state, and become polarised. Depending on the type of entanglement, a pair's photons will have either the same or opposite polarisation as one another.
This allows detection of an interception attempt. If a pair of received photons have not been intercepted, they will still be entangled when they hit the receiver, and so will always have, for example, opposite polarisation when they leave the quantum state. If one or both of the photons has been intercepted in transit, it/they will have already left the quantum state at some point and will no longer be entangled, so when they hit the ground receiver some will have the same polarisation, and some have different polarisation. That's when you know that someone has potentially fiddled with your data stream and you do not trust it.
I know it doesn't seem to make much sense, but this is the fun world of quantum mechanics. We know quantum theory is valid due to experiments in the lab and real life examples (i.e. semiconductor technology, and nuclear fusion due to quantum tunnelling in the Sun), just not really why...