- Can we use this to send large amounts of data around the world quickly? Can it replace intercontinential data links?
- Can we use this for interstellar communication channels of limited amounts of data?
- Can we use this to pass messages between two locations in a way that is immune to easedropping?
- What are other real-world applications of this?
Describing quantum phenomena with real world metaphors always breaks down if we carry things far enough. I'm going to use coin flipping as a metaphor to make a specific point, but don't assume this metaphor will still work if you try to extend it. To even begin to understand entanglement you really need to look at the math. That being said, let's proceed.
The Setup: (this explains how the metaphor is being made, but you can skip to the payoff if you just want the what without any of the why).
We can think of a pair of entangled particles as a pair of coins. If we flip each coin, we have a fifty/fifty odds of gettings heads or tails. This is what we normally think of, in the macroscopic world, as a random outcome (It's not really, but let's not go there). An entangled pair of coins behaves very unusually. The outcome of flipping one coin is related to the outcome of the other coin. For example, if one coin comes up as heads, the other will always come up as tails, or vice-versa. Let's say we separate the two coins by several light years and then flip them. The strange correlation will hold. For a non-Quantum particle there are several possible explanations for this behavior. We might think that, somehow, the measurement of one particle causes the outcome of the other article to change. However, time depends on reference frame. If the two coins are in relative motion to each other in the right manner, which particle was measured first is relative (There is no universally preferred reference frame). i.e. One observer might correctly say that the first coin was measured before the second, but another observer might see things reversed. So, which measurement is the cause and which is the effect? Another notion is that the outcome was preordained when the coins were made. I'd have to go into the math a bit to adequately explain this, but with entangled quantum particles you can create experiments that demonstrate this is impossible. Tests of Bell inequalities are especially notable for this. This is Einstein's "spooky action at a distance", a behavior exhibited by entangled particles.
The Payoff:
So, if a measurement performed on two entangled particles is like flipping a pair of coins, how can we use that to communicate. Well, we can't. Not directly. You see, we can't force a coin to come up heads or tails. If we look at the outcomes of just one coin they will always appear random and uncontrollable. It's when we talk to the guy with the other coin that we'll say, "Hey, I knew what you were going to get because of what I got!". So, classical communication, limited by the speed of light, is necessary to figure out what these correlations are. So forget about FTL communication. However, what about communicating secrets? Well, that's a whole other kettle of fish! It turns out quantum correlations are fantastic for communicating secret keys. Google quantum cryptography.
As for other applications, google quantum computing. Entanglement is absolutely intrinsic to this field. There are also applications in medical imaging and metrology (i.e. standards of measurements).
Maybe you could that same mechanism for superfast decision making communication in automated equipment. Drone dispersal, late stage missile targeting. Think shooting a bunch of missiles into the sky with a map of possible locations and then entanglement used to have each missile pick its target, no missile would hit the same target and no one would know which missile was going where at launch. Stuff like that works?
You could use it for frequency hopping on radios making tracing communication pretty difficult.
The closest use is probably quantum cryptography, somehow, I'd guess. But that's still not FTL communication.
The article might have glossed over that, but the researchers wouldn't have. Anyone who thought they had a way to send information FTL would be heralding it from the rooftops, because that, and not quantum teleportation or quantum solid-state whatever, would be the main story.
Why? Because FTL signalling inherently means causality is broken. Effects can precede causes. You can send information back in time. This is inherent in the geometry of the Universe, as predicted by Special Relativity, one of the best-tested and most-validated theories we have to date. Special Relativity is validated every time anyone uses GPS, for example, and the prediction that FTL implies travel back in time is inherent to what Special Relativity is.
So I'm not going to take you at your word. The supposed FTL neutrinos which turned out to be some loose cables show what happens when the scientific world even thinks that Special Relativity might need to be modified.
It could be used to ensure that 2 locations have the same random data. This is useful in cryptography.