It’s been a while since scifi showed us space ships with FTL (Faster than light) propulsion so we could get out of the solar system and into any potentially interesting place within our life spans. Given that Proxima Centauri, our best candidate for insterstellar travelling in distance ranking is 4.24 light years away, FTL ships might be our only option. However, how would we keep contact with people on that ship once their cell phones have no network coverage?
This question poses a double problem. First, we need a transmission medium (and possibly repeaters all the way back to ol’ Earth). This is obviously a problem itself if space is yet not colonized, but even if it were, all waveforms in the electromagnetic spectrum travel at light speed, which, in this particular case, might turn out to be quite slow. For example, Mars is usually ranging from 35 million miles away from Earth at it’s nearest to about 340 million miles at its furthest, so an electromagnetic based communication between Mars rovers and NASA may take from 3 to 30 minutes depending on the day. It’s only too good that those robots don’t need to be teleoperated, right?
Obviously, we need FTL communications too, but it’s easier said than done. In fact, scifi has come with a nice heads up for this kind of communication loosely adapting a phenomenon called quantum entanglement to its own needs. For example, in the Mass Effect game franchise from Bioware, EDI explains to Shepard how the Normandy communicates with the galaxy like this:
Despite all the maths, the basic idea under quantum entanglement is fairly simple: if you manage to get two quantums entangled, the actions of one will always reflect the other, despite the distance between them. Just imagine that you could separate yourself from your own shadow, but, still, it would do exactly what you do. If we manage to load that shadow inside a FTL ship and send it to the other side of the galaxy, whenever you raise your hand at home, your shadow would do the same over there, so, voila, instant information transmission or quantum teleportation, whatever you fancy most.
A non-entangled shadow doesn’t work …
Too bad reality doesn’t quite work that way. Indeed, some processes may produce two entangled quantum bits (qubits), meaning that they must present opposite states at all times. Think, for example, of a coin entangled with another one. If we toss ours and it goes heads, somewhere the entangled coin will go tails at the same time. If that coin is light years away, our toss information will have travelled faster than light. Since we know already that digital communications are long sequences of ones and zeroes, we could certainly work with this, but there’s a fundamental flaw in this approach: in order to send information, we must be able to control which side the coin falls every time. Imagine, for example, that we want to send an 8 to the other side, which is equal to 1000 in binary code. We need to toss the coin four times and get one tail and three heads, so the other coin will get the opposite result. The key issue here is that we NEED to toss, there’s no way we can simply set the coin one way or the other due to quantum mechanics: the state of an entangled qubit is always opposite to the other, but we don’t know which state it is until we measure it. Besides, it might be a good time to note that the first entangled quantum state is erased in the process …
Needless to say this communication concept is awfully similar to the famous Ansible in Ender’s game, Le Guin’s novels and even Stargate ancient communication stones, where two pieces of the same material are tangled to react similarly despite their physical distance.
Quantum entanglement has been labelled as teleportation -and used to justify exactly what you’re thinking about in Agents of Shield-, since it sorts of rebuild the quantum structure of a body in a different place, but reset the state of the original set (and, hence, it’s not cloning). Unfortunately, it only works with simple particles yielding only a few quantum states.
In fact, quantum teleportation works (limitedly): an international team led by the Austrian physicist Anton Zeilinger has successfully transmitted quantum states between the two Canary Islands of La Palma and Tenerife, over a distance of 143 km. The key for quantum communication thus far seems to be enabling a conventional communication channel to send in parallel information about the local quantum state, i.e. FTL received data patiently waits in storage 4.24 years to be decoded on Proxima centauri. Obviously, this method is not providing FTL communication any time soon 😦
 “Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it.” Terry Pratchett
 “The only things known to go faster than ordinary light is monarchy, according to the philosopher Ly Tin Weedle. He reasoned like this: you can’t have more than one king, and tradition demands that there is no gap between kings, so when a king dies the succession must therefore pass to the heir *instantaneously*. Presumably, he said, there must be some elementary particles — kingons, or possibly queons — that do this job, but of course succession sometimes fails if, in mid-flight, they strike an anti-particle, or republicon. His ambitious plans to use his discovery to send messages, involving the careful torturing of a small king in order to modulate the signal, were never fully expanded because, at that point, the bar closed.” Terry Pratchett