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NASA Sci-Fi

Can Quantum Entanglement Create Faster-Than-Light Communication? (mit.edu) 238

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."
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Can Quantum Entanglement Create Faster-Than-Light Communication?

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  • No (Score:5, Informative)

    by NotInHere ( 3654617 ) on Sunday May 01, 2016 @10:32AM (#52022477)

    TLDR: No.

    Next story please.

    • Re:No (Score:5, Funny)

      by Anonymous Coward on Sunday May 01, 2016 @10:36AM (#52022499)

      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.

      • by KGIII ( 973947 )

        Sure but you hadn't observed. Once you observed it, you locked it into that state. By extension, that post they made? That's *your* fault.

    • by mcgrew ( 92797 ) *

      TL;DR=="I'm aliterate. I hate to read.

      • Re:No (Score:4, Insightful)

        by Vreejack ( 68778 ) on Sunday May 01, 2016 @11:22AM (#52022673)

        In this case it means: "Stupid headline; clickbait that will lie or disappoint." The only possible news here is that NASA is doing something stupid, but I cannot be bothered to check for sure.

        Information cannot be delivered faster than Einstein's constant even using quantum entanglement. The concept is well-understood. Would you read an article about how NASA discovered how to make your car run more efficiently by using tap water instead of gasoline?

    • Re:No (Score:5, Informative)

      by michelcolman ( 1208008 ) on Sunday May 01, 2016 @11:18AM (#52022667)

      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 [arxiv.org]), 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.

      • Re: (Score:2, Funny)

        by Eunuchswear ( 210685 )

        I couldn't find a decent explanation that doesn't involve pages full of math.

        Welcome to Quantum Mechanics.

    • I'm just typing this before I crawl into my Primer tube at the storage depot to take a peak if FTL works in the future.

      Actually there's an interesting proof by David Wolpert that this sort of thing can't work the way you think it can. It sort of goes like like this in rough outline. There's only so much information that the state of the universe can encode. If you import information from another time frame to the current time frame you have to lose some information. He goes on to argue that information

      • With error correction you never get perfect transports, there is always the likelihood that all bits flip the right way such that the error code remains valid. The only thing error codes give you is to make errors less likely, to an arbitrary extent. They don't give you the ability to eliminate all errors. You can however make it so unlikely that the likelihood that an error happens within the next 10 billion years is less than 1%.

      • I'm just typing this before I crawl into my Primer tube at the storage depot to take a peak if FTL works in the future.

        Actually there's an interesting proof by David Wolpert that this sort of thing can't work the way you think it can. It sort of goes like like this in rough outline. There's only so much information that the state of the universe can encode. If you import information from another time frame to the current time frame you have to lose some information.

        Not sure I buy this. Setting the qbits on a machine in the past from "unknown" to "known" wouldn't create any more information than simply observing the bits in the past (without the time-sending). By Wolpert's argument, every time we observe something in an unknown state the universe has to forget something, or else put us in a wait queue. Unless of course the universe isn't currently storing its full capacity, in which case the argument fails anyway.

        OTOH, conservation laws may prevent physical time tra

    • by tnk1 ( 899206 )

      TLDR: No.

      Next story please.

      Yeah, not sure that this crap is. We already know that entanglement is useless for communication and we know why. Why do people keep pushing this click-baity misinformation? Stop constantly re-confusing people.

    • You are just saying that because you have a huge student debt from Astronaut school and this tech will make you redundant, an Astronaught.
  • by N3wsByt3 ( 758224 ) on Sunday May 01, 2016 @10:56AM (#52022581) Journal

    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.

    • Meaning, the moment to interact with your entangled electron or photon, it would 'set' its state, but in a random way.

      didn't we overcome the uncertainty principle when making quantum computers? [sciencedaily.com]

      • I'll grant you that is an interesting read. They're basically saying they can measure a wavefunction and yet it doesn't collapse by the measurement of it. (To be precise, they measure a property through the wave-function, namely if it's polarised or not.) It doesn't say they could measure what kind of polarisation had taken place, only that it did or didn't. So it doesn't denote that once it is 'set' in a state, it's not random anymore (you can't choose in front *how* it would be polarised, without collapsi

        • that's quite the verbose way of admitting you were wrong.

          • To be precise, it's a verbose way of acknowledging I *could* be wrong. ;-)

            Then again, if everyone would be willing to do the same thing on slashdot, debates would considerable improve around here. :-p

            The only thing I find strange, seen the dramatic implications of it, is that there seems to be no paper who has tried it out and confirmed FTL communication. I'm sure it would have been world-news and we'd all heard about it, if it was the case. And it's been 3 years since that paper...

            Thus, I'm leaving it open

    • Know what the most lovely thing is about science versus religion/superstition/mysticism/faith-based beliefs? Science can believe something completely absurd is possible, explore it, discover they're totally wrong about it, it was indeed utterly absurd as predicted, and not only is that okay, it's encouraged behavior. How many 'absurd' things has some researcher in the past believed, that the scientific community (and even the public-at-large for that matter) scoffed at, ridiculed and even ostracised the res
      • Amen! ;-)

        I would say you're partially right. Journeying on itself can be fun. However, at a certain point you have to draw the line. For instance, claims without (scientific) proof about subjects that we already know of that are impossible (in the sense that it breaks basic laws we otherwise already would have measured and observed it long ago, if true), is a futile endeavour. It becomes the realm of pseudo-science, and that does more damage to science than anything else. That's why claims like that of the

        • In any case, lets be sceptical until more experiments confirm or refute the claims of that paper.

          Scepticism is, of course, part and parcel to all true science.

    • Obviously, I am not a physicist, so I genuinely asking this.
      I get that the change of the state would be random and thus there is no way to predict how the state will change. But do you need to know?
      I mean lets say the ship was 10 light years away and the partner was here on earth.
      Let's say that we figured out a way to both measure a change in state instantly. How it changed isnt important, only that it did change.
      We also figured out a way to change the state when we want to.
      Could we not just use frequency o

      • You can't tell if the state has changed without measuring it. The first of the entangled pair of particles (one at home, one on your spaceship) to be measured will mean the other will be measured (when it is) in a complementary state. That's all that happens. We're not talking about some particle giving off a photon of light when its partner is measured or anything like that. Also measuring breaks the entanglement. Purposefully changing the state of one of them also breaks the entanglement. So you can't have a bunch of them that you keep on measuring, waiting for one of them to change state. It just doesn't work that way.
  • Cornodium (Score:2, Interesting)

    by mcgrew ( 92797 ) *

    I used quantum entanglement in a SF story I posted in my journal [slashdot.org] (a better copy without /.'s patented smart quote mangler is here [mcgrew.info]). I called them "jump radio" in the story.

  • I would love to find out where Mr. Shatner got the wisdom to make that insightful statement.

    Not to put him down, but his background as an actor and "writer" hardly gives him the background to understand what that statement means.

    I suspect that both he and our current Prime Minister have a publicist with at least an undergraduate degree in physics.

  • by Steve1952 ( 651150 ) on Sunday May 01, 2016 @11:04AM (#52022615)
    Can quantum entanglement methods be used to allow a web browser, while running an ad-blocker, to access Forbes? This might be real progress.
    • I run Ghostery and uBlock Origin in a Chrome incognito window for my regular browsing. Forbes first opens up to a welcome page. But every Forbes link after that opens up to the article without ads. Am I doing something wrong (right)?
    • In Google News you can easily customize the tool to avoid anything coming from Forbes.
  • by wonkey_monkey ( 2592601 ) on Sunday May 01, 2016 @11:08AM (#52022633) Homepage

    Slashdot reader StartsWithABang writes:

    Reader? Reader? I very much doubt StartsWithABang ever reads anything here.

    Can Quantum Entanglement Create Faster-Than-Light Communication?

    No, it can't. This has been known for years, and gets pointed out in every quantum story on Slashdot multiple times.

    If a headline asks a question, and the answer is known, I should think the last Slashdot could do is to put that well-known and proven answer in the summary.

    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."

    Does that have anything to do with the aim of FTL communication? Or did you just put it in because it had the word "quantum" in it?

    This week even 85-year-old Star Trek actor William Shatner cited quantum entanglement in a discussion of Star Trek's transporter technology

    And just when I thought it couldn't get any more tenuous...

  • by mbone ( 558574 ) on Sunday May 01, 2016 @11:13AM (#52022649)

    Suppose I have two marbles in my bedside drawer, one red, one blue. In the morning, I get up and put one in my pocket, leaving the other behind, but without looking at either. I then go to work, say on Alpha Centauri, 4 light years away (say in a NAFAL spaceship). At some point, I pull out the marble in my pocket, and see that it is red. I now know instantly that the marble in my drawer back on Earth, four light years away, is blue.

    Can that be used for communication? No. Quantum entanglement makes the choices more complex, but it doesn't allow for FTL communications any more than the marbles in my pocket do.

  • Subject says it all. Forbes' fuckery is what inspired me to switch from one to the other.
  • 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.

    From what I have read, there is nothing magical about quantum entanglement.

    Instead of photons lets use a coin. You take a coin and split it in half such that one half has the heads and the other tails. Now place each half into a separate sealed box. While doing this DO NOT LOOK AT THE COIN HALVES as this is where quantum entanglement claims to be magical and influential. Now send those boxes out to two locations anywhere in the universe. Now open one box, see what is contains and you will know immediately w

    • There are some experiments that prove the values are not set - but they cannot be observed without also randomising them in such a way that no information can be transferred.

    • The problem is it's already been shown that the particles don't have any hidden state as your coin halves do. As I understand it is more like having two coins which always come up on opposite sides when flipped. It really is weird and difficult to understand how it's possible, all we know if that it is. Regardless, it's still useless a far as communication goes.

  • NO MORE FORBES LINKS (Score:5, Informative)

    by Gravis Zero ( 934156 ) on Sunday May 01, 2016 @11:56AM (#52022813)

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

    • There are browser extensions that get rid of the splash screen. Here [tinyurl.com] is one for Chrome.

    • What about if we had a new movement to rewrite all the interesting articles on sites like Forbes. Only takes one person to do this and it saves a lot of time and frustration for the rest of humanity.

  • There are some theories, most prominently the De Broglie-Bohm theory (https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory) which assume that the Universe itself is inherently non-local.

    These theories are basically Aether theories (https://en.wikipedia.org/wiki/Aether_theories) which assume some kind of unknown medium (possible that medium is space itself). Do not confuse these with the Luminiferous aether theory.

    If there is such medium that can explain a lot of things eg. why the Universe appears t

  • From my limited understanding on the subject, the actual entanglement only allows you to know the state of the other particle at the far site when you measure yours. You can't actually change the state of either particle, which you'd need to be able to do in order to effect communication. However, it also seems like it's been proven that it's not because the states are determined when the particles interact -- experiments have been done to prove that the state of both particles is determined when either is
    • From my limited understanding on the subject, the actual entanglement only allows you to know the state of the other particle at the far site when you measure yours.

      Which introduces a problem of its own: since they can't tell you when they've sent a message, when you measure yours you don't know whether the result is a message or just the measured value of a qbit's state.

      I assume this is an optimization technique so the universe only needs to compute the states of the things that someone cares about.

      Yes - Just-In-Time content creation for the simulated universes we talked about last week.

  • The NASA report isn't about faster-than-light communications, it's about sending more bits per photon than current optical transmission systems, thereby transmitting data "faster" in the same way that LTE is "faster" than 3G.

    According to standard quantum mechanics, quantum mechanics cannot be used for faster than light communications. Now, I'm usually the first to point out that physics isn't mathematics; standard quantum mechanics may simply turn out to be wrong in the long run on this point. But so far, t

  • First law of media: whenever a news title ends with a question mark, the answer is no. So, FTL communication: nope, and entanglement can't help it.

    NASA-sponsored research at U. Illinois: use superdense coding, with some interesting twists (note to myself: read about it). That's no FTL, but usung fewer photons for communication than the number of bits communicated. Such technology may become applicable in a distant future.
  • What I think is interesting if it were possible to create a warp drive and people ended up scattered about the galaxy Internet of the very distant future could resemble one giant sneaker net of ships ferrying information.

    Also posting links to Forbes is a lost cause. We can't read them.

  • My browser is entangled with an ad-blocker and everything collapsed when Forbes observed it.
  • Working article link (Score:4, Interesting)

    by evilviper ( 135110 ) on Sunday May 01, 2016 @01:59PM (#52023427) Journal

    This link will work fine even with ad blockers:

    http://webcache.googleusercont... [googleusercontent.com]

    You can also change your user agent to Googlebot to workaround such shenanigans.

  • There is a catch, I can know what the remote state is after I discover the local state, but how do I go from that to the point where I can induce the remote state by forcing the local state. Once I can do this I do indeed have a faster than light binary data link. Perhaps I do not need to force the local state if my particles have more than one entanglement and those states are correlated so that I can improve my chances of guessing one state by discovering another correlated property. This allows me to dis
  • We could build intelligent space probes and send them to our nearest stars. If they are small we could send 5 to 10 each for redundancy. They would be as artificially intelligent as we could make them. Then they would answer a series of yes/no questions about the system. That way we could categorize interesting systems to investigate further.

    We could also send larger probes able to replicate and repair themselves such that they could investigate indefinitely. If the AI we sophisticated enough we could send

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