Can Quantum Entanglement Create Faster-Than-Light Communication? (mit.edu)

Slashdot reader StartsWithABang writes: If you were to send a space probe to a distant star system, gather information about it and send it back to Earth, you'd have to wait years for the information to arrive. But if you have an entangled quantum system -- say, two photons, one with spin +1 and one with spin -1 -- you could know the spin of the distant one instantly by measuring the spin of the one in your possession.
This "incredible idea to exploit quantum weirdness" for communication was the subject of a recent Forbes article [which blocks ad-blockers] as well as a NASA mission directorate. ("Entanglement-assisted Communication System for NASA's Deep-Space Missions: Feasibility Test and Conceptual Design".) And Friday MIT News reported a research team is now making progress toward capturing paired electron halves for quantum computing on gold film. "Our first goal is to look for the Majorana fermions, unambiguously detect them, and show this is it. "

This week even 85-year-old Star Trek actor William Shatner cited quantum entanglement in a discussion of Star Trek's transporter technology, arguing that "Although a lot of the concepts in science fiction are absurd to our Newtonian minds, anything is possible because of the new language of quantum physics."

Comments

No

[NotInHere]

TLDR: No.

Next story please.

Re:No

[Anonymous Coward]

IDK, I was able to know pretty much exactly that this was going to be the first post, several minutes before the post actually showed up.

Re:No

[michelcolman]

Nothing about faster than light communication (which is still impossible as far as we know, and highly unlikely to ever be discovered as it would allow sending messages back in time if our current understanding of relativity is correct).

What they are researching, is sending a larger amount of information over a long distance through space with the same number of photons, by using entanglement to reduce noise somewhat. The idea is quite complicated, google "quantum-enhanced classical communication" for more details, you can find a few related papers that are not behind pay walls (like here), but I couldn't find a decent explanation that doesn't involve pages full of math.

It's definitely not faster than light. Just a clever trick to make it a little (not even a lot) more likely for a message to arrive intact without errors.

FTL communciation with entanglement not possible

[N3wsByt3]

I used to think this was an option too, but the more I read about it, the more it became obvious that it wouldn't work. This is because, while you would easily and immediately have an influence on the paired quantumdot at Earth, even if you were 10 lightyears away, there is no way to direct or guide to any particular state in front. Meaning, the moment to interact with your entangled electron or photon, it would 'set' its state, but in a random way.

So the information encoded in entanglement is only extractable when you look at correlations between measurements on both the entangled systems. So to access that correlation information, you would need communication anyway, and that communication could not be FTL. If you only look at either system, but not the other, then you need no such communication, but you also can extract no information from the entanglement. This is actually a good thing, because much of science is done by ignoring entanglements, and the reason we get away with that is the information we are ignoring cannot interfere with our interpretation of the results of our experiment.

Suppose we split up two qubits in an entangled |00+|11state, where we've established that Alice is going to measure two overlapping bell curves with their double-slit experiment.Suppose Bob likes wavy interference patterns. The rules of quantum mechanics allow Bob to do, on his qubit, any unitary transformation like |0|112|0+12|112|012|1.

This takes our state to:
14|00+14|01+14|1014|11
Now supposing that Bob measures his qubit as 0 or 1, then Alice must measure either the wavy interference patterns 12|f0(x)+f1(x)|2 or 12|f0(x)f1(x)|2.

Bob can thereby instantaneously change, from a quantum perspective, what the outcomes of Alice's measurement are going to be.

Alice's wavefunction must change instantaneously and might even change retroactively: she may have already measured her qubit before Bob does this unitary transformation and measurement: nevertheless, to satisfy the predictions of quantum mechanics, her measurements must be consistent with Bob's manipulations. But that can't send messages. Because this thing that Bob has done is not directly visible to Alice. That's for a couple of reasons, the first being that this only generates one photon of results on the double-slit screen, which isn't enough to see the pattern! But suppose we measure lots and lots of these qubits to try and see the pattern: then the problem is that Alice doesn't know which ones Bob measured as 0 or which ones Bob measured as 1. Since there was a 50/50 chance of Bob getting either, what Alice sees is therefore:
14|f0(x)+f1(x)|2+14|f0(x)f1(x)|2=12|f0(x)|2+12|f1(x)|2.

Alice therefore still measures two overlapping bell curves, overall!

Where are the interference patterns?! That is very simple: when Bob and Alice compare their measurements in the first case, Bob's 0-measurement can be used to "filter" Alice's patterns into 12|f0(x)|2,
the bell curve of photons which passed through only the first slit, and his 1-measurement filters the results to give 12|f1(x)|2,

Bob's transformation then changes how he can filter Alice's patterns: Alice's overlapping bell curves are now made up of the ones he measured 0
for, which describe one wavy pattern, and the ones he measured 1 for, which describe the other wavy pattern, and they add up into the non-wavy pattern.

NO MORE FORBES LINKS

[Gravis Zero]

seriously, please reject all stories with links to forbes from now on.