Like, keep parsing the incoming information until you see a period (for example).
(I know it's not using actual characters, just using the idea to illustrate the point).
There's no parsing; it's all or nothing.
Entangle some matter, give half of it to the space team and then have inter-stellar walkie talkies?
Edit: or can the communication only happen once and then you need to remeasure over classic communication?
As I said, no. How would you relay your measurement results in real-time? Without those measurement results, the receiver would in essence just hear white noise.
That's the perplexing part of entanglement. Somehow it feels like information is instantaneously transferred from A to B, yet the information content is somehow zero so can't be used for proper communication.
When measuring one particle of an entangled pair and you get say "spin up", you know immediately that if someone measures the other particle (with the same measurement settings) they'll get "spin down", and vice versa.
The chance that you get "spin up" or "spin down" is 50/50 and, as far as we know, cannot be affected or determined in advance.
So, on the receiving end, they measure some random combination of "spin up" and "spin down". Without anything else, this information is for all intents and purposes noise.
What you can do however, is to send a message using regular means with what you measured: "up, down, down, up, down". Ok, at least now they can check that what they got was the exact opposite. However that still doesn't tell them anything.
So instead what you do is that you change the measurement settings, and send via regular means not just your measurement results but also your measurement settings. So you'll send "H left, V down, V up, H left, H right". The recipient will then take the measurement settings (H or V) and measure the entangled particles in the same way you did, and then note down that they get the opposite.
Note now that you suddenly got a way to communicate some actual information. By agreeing in advance that a Vertical measurement means 0 and a Horizontal measurement means 1, you can send information to the recipient.
However also note that you had to make a measurement of your particles and then send the results using regular means, limited by the speed of light. So why bother with this complicated setup? Why not just send the data without all this entangled stuff?
And indeed, for just sending plain messages it makes no sense to use entangled pairs.
However as I noted in my other post, the inability to clone entangled states means an eavesdropper can be detected using the entangled setup.
As I've understood it, to "listen in" the eavesdropper has to destroy the entangled state by measuring it, and there's no way to perfectly clone the entangled state before doing that.
The recipient can compare the entangled data with the measurement results (sent via classical means) and detect statistical inconsistencies if there is an eavesdropper.
edit: I see their page[1] mentions quantum metrology, which I found reference to in a page[2] describing work to improve GPS and similar detection using quantum entanglement. Not sure if it's directly related but seems like there should be room for some interesting work using this quantum network in this area.
[2]: https://news.engineering.arizona.edu/news/quantum-entangleme...
Why is that? This keeps happening. Quantum entanglement is not a new concept. It's almost certainly older than 99.9% of the people on this site. Yet the myth that it could enable FTL communcation continues to persist.
Imagine that you have 2 coins and give one to someone on earth to flip and one to someone on the moon to flip. The outcomes in either location is random 50/50, but interestingly they are perfectly correlated (H<->H, T<->T). When you flip a coin you don't have the ability to pick it's outcome. The only thing you can pick is whether or not to flip it at all. So, imagine you want to communicate one bit of information from earth to the moon and decide that a 1 will be encoded as "flip the coin" and 0 as "don't flip the coin". When you're standing on the moon and want to reveal the information you flip the coin and see e.g. H. There are two ways this could have happened: either the earth coin had already been flipped and showed H or the earth coin had not yet been flipped and you just randomly got a H. In other words, the outcome by the flip is useless by itself.
"2 generals command 2 armies hundreds of km apart. They want to attack a common enemy, there are 2 options, A) And all-front attack. B) From the flanks. The generals want the plans to remain uncertain until the last second before the attack. So from an intermediate point, they send two "entangled coins" , one to each general, the coins will arrive at both sites at the exact start of the battle.Both will show the same face when "measured". The generals have agreed previously that if they turn out "heads" they will both attack from the flank, in the other case, they will do a front-attack.
Of course you dont need a quantum system for this, you could have agreed on other stuff (like it if it is raining that day at certain place or sending a framed coin by regular mail) but I think the quantum solution is the more elegant, assuming no 3rd party snooping.
So really it just front-loads that portion (I.e. removes it from consideration as part of the proposed solution) instead of allowing it to slow down solving the overall problem. It requires precomputation/agreement beforehand, rather than during the time allotted to the problem.
The speed of that precomputation would still be unchanged, and still be the slowest portion.
However, as he said, in this situation the two generals could have agreed on something else, like if it was raining or not.
In fact, something they could have done is to flip a coin, and split with a copy of the result, which they only look at when they launch the attack. It would have the same effect.
With a random variable (the coin flip), that is hidden until revealed, we achieve the same results as quantum mechanics.
Scientist call them "hidden values" and Einstein hopped we could explain the "spooky action at a distance" with such hidden variables. But we can't, Bell proposed an experiment with entangle state which measurement could not be explained by such hidden variables, and Aspect did the experiment and obtained the predicted results.
So there exist situation where we can use entanglement to achieve better results, for example in "non-local games", where players sharing entangled state can win with probability 1, when "classical player" with probability < 1
Do you have an example for this? This is really interesting
Yes but the difference is that in this case, the plan already exists from the moment the coin is flipped until the result is revealed to the generals. In the QM case no one (not even God) knows what the result will be until it is actually measured,but once that happens the result is known "instantly" at both places (assuming both coins arrive at the same time), so in that sense is a FTL communication (of course it is not real communication)