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

[mcgrew]

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

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.

Re:No

[Vreejack]

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

[Anonymous Coward]

a recent Forbes article [which blocks ad-blockers]

So why are you posting this shit? We're going to disable adblocking so we can be exposed to Forbes ad-delivered malware, just to see some stupid click-bait article?

Jeez. Please fuck off and die already.

Re:No

[KGIII]

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.

Re: No

[im_thatoneguy]

Except that you get into Uncertainty Principles which mean that the information you gain is random. It's like a random bit generator. Now, take that random bit generator and increase the number of bits... still random.

Re:No

[Anonymous Coward]

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.

That was clear from Ethan "StartsWithABang" Siegal and the attempt to sneak a Forbes malware link past our deflector shields. (And you did right by not bothering to check.)

Mr. Siegal, I know you don't read this because you don't participate anywhere, you just shill your splog all over Slashdot, Fark, and every other social site you can try to get exposure on, but please, do fuck off.

Re:No

[tnk1]

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.

Re:No

[tnk1]

We don't know everything about the universe. We also should discuss the possibility of FTL.

What is wrong with this is that we've already discussed entanglement in regard to FTL and we already know it doesn't work that way. This is like looping around to the same wrong answer time and time again. Let's move on to something that hasn't been ruled out.

Re:No

[minogully]

So, from the article, if you just "read" the state, it'll remain entangled, but if you "set" the state, then it breaks the entanglement and the other side's chances become independent...

So what if you did this...
Use many quantum entangled photons instead of just one. Read them all, then "set" the ones that aren't in the state that you are trying to achieve to break the entanglement of these ones with the incorrect states.

Shouldn't that you give you 75% of the photons on the other side with the state that you are trying to communicate?

Re: No

[amRadioHed]

No, it clearly can't no matter how many marbles you have.

Re:No

[dsmatthews9379]

You are just saying that because you have a huge student debt from Astronaut school and this tech will make you redundant, an Astronaught.

Re: No

[sexconker]

No, it can't. The clock starts when you create the entanglement / separate the marbles.
No information can be obtained later that couldn't be obtained immediately after the entanglement / separation of the marbles.

Re:No

[Eunuchswear]

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

Welcome to Quantum Mechanics.

Re:No

[david_thornley]

Nope. Suppose we did this by having pairs of envelopes, and each pair would have one black and one red card in it. We send envelopes to A and the paired envelopes to B. Suppose A wants to send "black", so A leaves envelopes with red cards alone and replaces black cards with red. This will tell B nothing. (In your example, there's another issue. How is A to know which entanglements to break? A has to look at the entangled particles to determine which are which, and that tells A what B sees.)

Cards and envelopes are a reasonable analogy in the usual case of entanglement communication, in which entangled pairs will always have opposite values. Once you start doing anything more complicated, the analogy breaks down badly.

Re:No

[jfengel]

It's a bit more complicated than that, but the conclusion is correct.

You're describing a local hidden variables theory, in which the particles already have a definite value at the point where they were entangled. That doesn't quite describe reality; with some subtle experiments you can see that they interact in ways slightly different from ones that are already set. But that difference still doesn't allow you to communicate.

Re:No

[Tablizer]

it means: "Stupid headline; clickbait that will lie or disappoint."...Information cannot be delivered faster than [light]

Seems bullshit travels faster than light

Re:No

[misaltas]

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).

Huh? What? No!! Relativity suggests no such thing.

Even *IF* entanglement allowed for one "controlled" bit of information to be sent FTL (which even this article admits it cannot, after it implies to those with short attention spans that it can), nothing in this scenario suggests anything is moving "back in time".

Just because the sound of a distant drum reaches you faster by wire than by air, doesn't mean you heard the drum before someone starting beating it. Ok, maybe that's a bad analogy. Still... even if information can be found to move FTL does not mean it moves faster than time.

Re:No

[misaltas]

>>does not mean it moves faster than time
sorry, I meant "backward in time" not "faster than time"

Re:No

[michelcolman]

Relativity says that simultaneity is subjective. One observer will say that lightning strikes two ends of a train at the same time, while another observer will say that the front was struck first, and yet another will say that the back was struck first. I'm not just saying that they see the strikes at different times. They will come to this conclusion based on the time they saw the strikes, the distance to the strikes, and the speed of light in their reference frame (which is always c relative to themselves).

What's more, all of them are correct. There is no prefered reference frame. As long as nothing can travel faster than light, this never leads to any real contradictions. Who cares which lightning strike hit first, if the different strikes were far enough apart so that neither could have possibly influenced the other. Causality is still preserved, simultaneity at different locations is just a matter of labeling.

Things get more complicated, however, if you could send information faster than light. Let's say Alice could send a signal to Bob "instantaneously", meaning Bob's reception is simultaneous with Alice's transmission. A different observer, traveling at a significant speed, will correctly say that Bob received the signal before Alice sent it. This might not immediately cause problems because Alice and Bob are far apart, however things get more complicated when you start sending messages back and forth using different reference frames.

Example:
Alice and Bob are 10 light minutes apart from each other, but not moving relative to each other. They synchronize their clocks: Alice sets her clock to 11:30 when she sees 11:20 on Bob's clock, taking the 10 minute time delay into account. At 11:40, Bob sees 11:30 on Alice's clock. They both agree that this means their clocks are synchronized, since it takes 10 minutes for light to travel from one to the other.
Now, at 12:00, Alice "instantaneously" sends a message to Bob who receives it at 12:00. Looking at Alice through his binoculars, Bob can still see her clock indicating 11:50 and it will take another 10 minutes before he can see her type the message, but his magical entanglement transmitter has already received it.
Imagine at the same time, at 12:00 on Bob's clock, Carol happens to be passing by Bob at high speed, moving away from Alice at a speed of 60% of the speed of light. Of course, in Carol's frame of reference, she is standing still while Alice and Bob are moving with 60% c relative to her. The distance between Alice and Bob, in Carol's reference frame, is only 8 light minutes due to Lorentz contraction. Carol can see exactly the same image from Alice's clock ("11:50"), but since Alice is moving away from Carol at 60% c, this means the clock image must have left Alice exactly 5 minutes ago. At that time, Alice was 5 light minutes away and she has traveled a further 3 light minutes away in the 5 minutes after that. In Carol's reference frame, light travels at a speed of c relative to Carol. So Alice's clock was indicating "11:50" 5 minutes ago. Due to time dilation, her clock is ticking more slowly (80%) so in those 5 minutes it will have advanced to 11:54. So that's what Alice's clock is indicating "now", and Carol is entirely correct when she says that, in fact, the two clocks are not synchronized at all. There is no objective reason to say who is right, different observers can agree to disagree on whether or not two clocks are synchronized. Alice and Bob say the clocks are synchonized, while Carol says that Alice's clock is 6 minutes behind Bob's, and that's OK.
This does mean, though, that from Carol's point of view, Alice has not even sent the message yet. Her clock is only indicating 11:54 while she will only send it when her clock shows 12:00. Bob received the message before Alice sent it! But it gets weirder: let's say Bob gives the message to Carol as she is passing by, and she "instantaneously" sends the message back to Alice. Bingo, Alice receives the message at 11:54 (which is "now" according to Carol) befor

Re:No

[minogully]

How is A to know which entanglements to break? A has to look at the entangled particles to determine which are which, and that tells A what B sees.

How is needing to look at each entangled particle first an issue? Can you not look at them all first, then "set" after you look?

Also, the article states that setting breaks entanglement leaving the chances of finding either red or black on the B side put to random.

Unless this is an oversimplification of how it works, I'm not seeing the issue here.

Using your cards analogy, starting with say, 100 envelopes:
1) A reads all of the envelopes. Sorts them with all of the red in one pile and black in the other. It'd be a 50/50 split.
2) A takes the black cards and replaces them with red. This breaks the entanglement for these cards, which according to the article resets what cards B has in these envelopes. Now A knows B has the original 50% black cards that were never touched, and then because the entanglement was broken, the remaining cards for B are black and red split 50/50. That's 75% black and 25% red.
3) B reads all of their envelopes at a pre-specified time. Looks to see which are 75% to determine what A was trying to send.

Re:No

[painandgreed]

We don't know everything about the universe. We also should discuss the possibility of FTL.

What is wrong with this is that we've already discussed entanglement in regard to FTL and we already know it doesn't work that way. This is like looping around to the same wrong answer time and time again. Let's move on to something that hasn't been ruled out.

Well, there are several books on the subject out there by respected physicists. Sticking within stuff we have reason to believe actually might exist, it's still far out stuff and no practical way to test it. Technically, in things like hyperspace and worm holes, it's usually not even FTL as nothing is travelling faster than light, but rather just taking a shorter path to get to where it's going. We see this effect all the time in gravitational lensing where two light-like paths exist to the same object but they are different lengths. Still, we have no idea if extra dimensions really even exist let alone a practical way to go through them, and worm holes and warp drives require massive warping of Reinmannian space in such ways that the math may work out, but there's no conceptual way to actually do it and it may not even be possible if the structures needed (exotic matters, miniatures black holes, cosmic threads, etc) can't exist. Space can warp, but it's damn hard to make it do so and we might as well consider it flat for these purposes.

Re:No

[david_thornley]

I'm getting a touch over my head here, but now that I've thought about it, I think just checking the value breaks the entanglement.

Suppose we're checking electron spin, which we'll separate into up and down. There are only two values of electron spin. Now, suppose we rotate our detector at some angle or other. If both the sender and receiver rotate by 45 degrees, they'll get opposite readings, but obviously not quite the same ones. However, we can only measure at one angle. If we try measuring up-down and then left-right, we'll get random left-right values that are not correlated, meaning the entanglement has been broken.

This is one of the places where quantum physics gets REALLY weird, since we know the electrons don't have any hidden spin axis or other such thing, from Bell's Theorem. They're just opposite each other.

Re:No

[misaltas]

All fair points and all great examples, and I appreciate the discussion. Fascinating stuff.

"magical entanglement transmitter" -- what a great name for it! :-) (let's use "MET")

Despite everything you said, it's still true that some of your examples above deal with *apparent* relative simultaneity, not absolute simultaneity (which can be proven btw, but is a different issue). And while another of your examples does consider time dilation that occurs as a result of relative movement, (both well-known and long proven phenomena,) still nothing in any of your examples indicate anything moving backward in time. Nothing suggests that our MET is allowing for a message to be received (in an absolute sense) before it's been sent (in an absolute sense). The MET doesn't create a paradox.

>>Now, at 12:00, Alice "instantaneously" sends a message to Bob who receives it at 12:00. Looking at Alice through his binoculars, Bob can still see her clock indicating 11:50 and it will take another 10 minutes before he can see her type the message, but his magical entanglement transmitter has already received it.

Yes, the MET has caused Bob to receive Alice's message, because she sent it at 12:00 and he received it at the absolute synchronized 12:00. When he looks at Alice through his binos, he sees what she looked like at 11:50, and yes it's going to take 10 more minutes before he sees her type it. That doesn't mean she hasn't sent it yet. It only proves that light bouncing off Alice as she typed it took 10 minutes to reach Bob's binos. If Bob at 12:00 uses his MET to send a reply message to Alice, she's not going to receive it at her 11:50, she's going to receive it at her 12:00. Using his binos, Bob will see her receive the MET message 10 minutes later, but it still was received absolutely at the same synchronized 12:00.

1. Nothing in your example shows anything going back in time.
2. Lorentz contraction is not absolute contraction, it only appears such to an observer moving at some speed relative to the thing that appears to be contracted.
3. Relativity paradox and time dilation only explain things speeding up and slowing down in time due to movement relative to one another, it doesn't suggest or explain anything going back in time, even if this MET device allows information to be passed simultaneously in an absolute sense. Besides, the point I'm making about a MET not allowing messages to be received before they are sent is logical whether the two communicators are stationary or moving relative to one another.
4. "Relativity of simultaneity" only covers apparent simultaneity, regardless of whether or not two or more events/observers are moving or stationary relative to one another. The fact that two clocks synchronize and then get out of sync due to time dilation caused by relative movement breaks those clocks' ability to measure absolute simultaneity, but it doesn't prevent a third party from doing so.
"There is no preferred reference frame.", no, but there is such a thing as absolute simultaneity, and it can be measured and proven.

The logic of these points can be shown by adding a 3rd observer. And let's take relative movement out of this for a moment.

Imagine A, B, and C as points on an isosceles triangle, each vertex of the triangle being 10 light minutes apart with watches that are absolutely synchronized against a point D, also exactly 10 light minutes from A B and C. All 4 points are stationary relative to one another. It is now absolutely 12:00 at ABC and it's 12:10 at D. Forget about D now. It was only there to sync ABC's clocks to absolutely be the same time.

A and B have telescopes aimed at each other, and looking thru each telescope at 12:00 reveals a clock at the other end that says 11:50 even though at that same moment, A's clock appears to A to be 12:00, and B's clock appears to B to be 12:00. C has two telescopes looking at A and B, and at 12:00, C sees both A's and B's clocks to b

Re:No

[michelcolman]

Relativistic effects are not "apparent", they are real. If one of two twin brothers flies away at high speed and then comes back, he really will have aged less. This has been proven with atomic clocks on board of Concorde airplanes and has to be taken into account by GPS navigation systems (along with gravitational effects on top of that). Lorentz contraction, too, is very real. Let me give you one example of the latter, which is also a great example of the relativity of simultaneity (real simultaneity, not just apparent).

Two trains are approaching each other head on on a single track. Both are 100 meters long when they are at rest. Between them, there's a small train station with a switch on every side and a section of double track in between, allowing trains to pass each other. Problem is, this section of double track is only 80 meters long. The trains can't possibly pass each other there, right? Wrong. All they have to do is accelerate to 0.6 c. The Lorentz contraction shrinks the trains to 80% of their normal length, and they can pass each other just fine. The front of the first train passes the back of the second train on one side, while the front of the second train passes the back of the first train on the other side, at exactly the same time.
It gets more interesting, though, if you look at this from a point of view on board one of the trains. From that point of view (and that's not just a perception, but your reality which you can check using any measurement method you like), your train really is 100 meters long since it is not moving relative to you. The section of double track that is coming towards you, however, is traveling at a speed of 0.6 c towards you and has therefore shrunk from 80 meters to just 64 meters! How can you possibly pass the other train then? Fortunately, if you measure the speed of the other train, it is traveling at a speed of just over 0.88 c (the "relativistic addition" of 0.6 c + 0.6 c). That means it has contracted to a mere 47 meters in length. This is where it gets really interesting: from your point of view, the front of your 100 meter long train reaches the end of the 64 meter double track exactly when the end of the 47 meter long train has passed that switch. That train still has 17 meters of track to go, which it will cover in 17 m / (0.88 c - 0.6 c) = about 0.2 microseconds. That gives the back of your 100 meter long train just enough time to clear the other switch before the front of the other train gets there. (100 m - 64 m) / (0.6 c) = the same 0.2 microseconds
See what happened there? Two observers do not agree on the length of the trains, nor on the simultaneity of the passages on the two sides, yet both agree that the trains pass each other just fine. From one point of view, the two trains are 80 meters long and pass each other simultaneously on the 80 meter track. From the other point of view, the 100 meter train just misses the back of the 47 meter train on one end of the 64 meter track, and a very short time later the back of the 100 meter long train misses the front of the 47 meter long train at the other end.

And most importantly, neither of these points of view is better than the other! In each reference frame, some things are shrunk, and the passage would not work without this. Which parts are shrunk, and which parts are "normal", depends on the observer. But no matter what point of view you take, the effects are real because without relativity, those trains could never pass each other. Also, relativity of "real" simultaneity is vital to the solution of the paradox.

Now, if you can send a message "instantaneously" from one switch to the other in the station's reference frame precisely when the trains are passing each other, and then send it back "instantaneously" from the point of view of the train that's just reaching that second switch, it will have traveled back in time because at that moment, from the point of view of the train, its back end has not reached the first switch yet.

By the way, this is a variation of the l

Re:No

[misaltas]

Sounds like we agree with the fact that a MET wouldn't cause any "you received it before I sent it" type of paradoxes so long as no one in the scenario is moving relative to one another.

Ok, first... relatively stationary things:

>>I think you misunderstood the setup. You are only talking about Alice and Bob, but left out the crucial third participant Carol

I did that on purpose. Meaning, I was trying to simplify the variables so that my example can remain focused on whether or not a MET device sending something FTL might run the risk of exhibiting the "received before sent" paradox. I still kinda stand behind the idea that, as long as no one is moving relative to one another, the fact that a MET message goes faster than light, doesn't mean it goes backward in time, despite the fact that speed-of-light observations of the actions might make it appear so.

Ok, onward to things that are relatively moving...

While my mind is still not seeing anything in your examples where something went back in time, I'll concede that I guess my understanding of all of this is incomplete. Especially the spinning example. And I'll admit while I remember the ladder example from school, I was always pretty convinced it was only trying to explain "apparent" size/location/timing. I understand speed of light. I understand time-dilation of things moving relative to other things (i've always found the twin paradox easy to understand), and I understand perfectly how these things are proven and well known as measured by airplanes and how GPS satellites/receivers rely on the speed of light in order to work at all. And I was thrown a bit when many (but not all) of your initial examples, and references you included, deal with and explain "apparent" simultaneity. Like, two things that are absolutely simultaneous by someone in the same frame as the events, may actually *appear* to take place before or after one another to other observers dependent on their relative location and motion.

In other words, I still don't get it *yet*, because some of your earlier examples seemed to be conflating things that are apparent with those that are absolute, but then later examples do distinguish between them. I do however stand by (so far) my logical postion that there *is* such thing as absolute simultaneity, as long as we don't confuse it with our ability (or inability) to measure or verify such simultaneity when things are moving.

Off to read more now. You put a lot of time into this, and I appreciate that, and I hope others who read it can benefit from it like I have. Time to stretch my mind a little on this before I object any further.

Re:No

[michelcolman]

You talk about "apparent" simultaneity as apposed to real simultaneity, but actually "apparent" simultaneity is the only kind of simultaneity that exists. I think that's the crucial bit of understanding you're still missing. Einsteins's big discovery was not the Lorentz transform (which was, obviously, named after Lorentz for a reason as he discovered it much earlier) but the realisation that appearances (things appear to shrink, clocks appear to tick more slowly, clocks appear to be out of sync) are actually real.

"Simultaneous" means: having the same time coordinate in the system of coordinates that you happen to be using. If one observer puts a label "12:00:00" onto two events in two different locations, that means he considers these to be simultaneous. Somebody else will put different time labels onto those events and say one occurred before the other.

The most important thing about relativity is: that really is all there is! People put labels onto things and use them to do calculations. Reality doesn't care, it only cares about actual interactions and, presumably, causality, but not where and when they occured precisely. They don't have "true coordinates", not in space and not in time. There's no such thing as absolute simultaneity, there can only be perceived simultaneity because no other kind exists. It's like absolute speed, there's no such thing, speed can only be measured relative to an observer.

If two observers with a different speed measure the speed of a particular ray of light, they will both measure it to be c relative to themselves, and therefore something other than c relative to the other observer. This means they disagree on the speed of that ray of light, and will therefore also disagree on when that ray of light left its source. One will say it left there yesterday, the other will say it left there two days ago. Both are correct, and it makes no sense to ask "but when did it really leave". When you ask "when", you're asking for a time coordinate, and you can only give that time coordinate if you pick a reference frame first. Otherwise the word "when" has no meaning. The answer to "when did the ray of light leave" can only be "it left yesterday if you use the first observer's coordinate system, or the day before yesterday if you use the second observer's coordinate system". When did it really leave? I just told you. There is no other answer.

If you look at the Lorentz transform ( t' = (t - v*x/c^2)/sqrt(1-(v/c)^2) ), it clearly contains an "x" in the transformation formula for time. Think about that for a moment. You know that moving clocks tick more slowly, hence the sqrt(1-(v/c)^2), but what's the x doing in the numerator there? It means that two events that are simultaneous for one observer (same t, different x) will have two different time coordinates t' for another observer and will therefore not be simultaneous from his point of view. Motion tilts the axis of simultaneity but since no observer is in any way better than any other, they are all "correct".

My point with the MET examples is that, although a message may be instantaneous for one observer, it travels back in time from a different observer's point of view and these observers are both correct.

When describing his special theory of relativity, Einstein didn't just say that the speed of light was the same for any observer. He actually said all the laws of physics are the same. In my example with Alice, Bob and Carol, Carol's view of the universe is just as correct as all the others. If Alice can send an instantaneous message to Bob in her reference frame, there's no reason why Carol wouldn't be able to send a message that arrives instantaneously in her reference frame. Both reference frames are just as valid, Carol is allowed to say that she is standing still while Alice and Bob are moving. Yet she can witness the transmission of the message from Alice to Bob and the only conclusion she can come to is that that message did, in fact, travel back in time. And from th

Re:No

[RespekMyAthorati]

Relativistic effects are not "apparent", they are real. If one of two twin brothers flies away at high speed and then comes back, he really will have aged less.

Which has absolutely nothing to do with "time going backwards".

Assume that I am "A". If I send a message to "B", then my reference frame is indeed "preferred" since the only concern regarding
"time going backwards" is whether I received a reply from B before I send the original message.

It doesn't matter a damn how B or C perceive the event. Since I sent the message, it is my perception, and mine alone, that matters.

Re:No

[RespekMyAthorati]

Einsteins's big discovery was not the Lorentz transform (which was, obviously, named after Lorentz for a reason as he discovered it much earlier) but the realisation that appearances (things appear to shrink, clocks appear to tick more slowly, clocks appear to be out of sync) are actually real.

Again, none of this has anything to do with "time going backwards".
The claim that "all reference frames are equally valid" is meaningless, since "validity" is a philosophical concept that has nothing to do with physics.

Re:No

[michelcolman]

In the example I gave, Alice sent a message to Bob, who passed it to Carol, who then sent it back to Alice. Alice received the message before she sent it. She sent the message, and her perception says that she did indeed receive it before she sent it.

Her perception is that the message traveled instantaneously to Bob, and was subsequently sent back in time by Carol.

Carol's perception is that the message traveled back in time from Alice to Bob, then traveled instantaneously back to Alice.

As usual with relativistic paradoxes, different observers describe the same events in a different way but confirm the same actually observable result: Alice receives the message before she sent it.

The question about why instantaneous transmission enables messages to travel back in time is described here as well.

Re:No

[michelcolman]

With "valid", I mean you can do all your calculations in that reference frame using all the same physical laws as any other observer, and make valid predictions that can later be verified to be correct.

That's just basic special relativity, and has been verified extensively.

I'm not saying time is going backwards. Just that, if you could send a message faster than light, you could also send a message back in time to yourself via a third person. That makes it rather unlikely for faster than light transmission to be possible.

Re:No

[misaltas]

Thanks. I really appreciate the continued replies and additional information.

I think perhaps I'm about to be the first person on an interwebz discussion forum to admit that, when it comes to this topic, the stuff I don't know and don't understand turned out to be greater than what I thought I knew and understood.

It's pretty clear that I have a lot more reading and learning and wrapping my head around this to do (and a few more lightbulb moments to experience) before I go poppin' off with "what, huh, no" about what your said in your original reply.

Thanks again for all the info, examples, and references.

Re: test it

[Anonymous Coward]

They already have tested it, and it can't go faster than light. Apparently some people haven't gotten the message.

Re: test it

[nanoflower]

Can it work when passing through the Earth? If so then it still has value as a communication technology that won't be blocked by objects in space or the rotation of the Earth.

Re:hmm...

[KiloByte]

The basic problem is that as it stands there is no way to tell if what one detects is random noise or a message.

Do you mean the communication or the article?

FUCK ETHAN SIEGEL

[Anonymous Coward]

What in living hell is that dildo Ethan Siegel (AKA StartsWithABang) doing spamming his malware-ridden Forbes articles (which he gets paid foor here again?!?!?!

Fuck you Ethan.

Fuck your Stupid Beard.

Fuck your self-aggrandizing blog.

And oh, die while you are at it. Painfully if possible.

Re:FUCK ETHAN SIEGEL

[Pikoro]

Generally, those aren't his entire articles. They're summaries, with links back to Forbes. It's a holding spot so he can double dip on ad revenue.

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.

Cornodium

[mcgrew]

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

Re:Cornodium

[nickersonm]

Not an Ansible?

Shatner really said *that*?

[mykepredko]

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.

Quantum entanglement methods for accessing Forbes?

[Steve1952]

Can quantum entanglement methods be used to allow a web browser, while running an ad-blocker, to access Forbes? This might be real progress.

Re: FTL communciation with entanglement not possib

[Anonymous Coward]

So is Bob fucking Alice or what? She is such a tease. And don't get me started on those middlemen.

Where to start with what's wrong here...

[wonkey_monkey]

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...

No

[mbone]

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.

Re: FTL communciation with entanglement not possib

[N3wsByt3]

Well...when fucking or being fucked, there is always some entanglement involved...

Re:Anyone that says 'no'

[jeffb (2.718)]

Well, I also can't prove that you aren't capable of reaching out with your thoughts, grabbing the Moon, and hurling it into the Sun.

However, the preponderance of evidence strongly suggests that you can't. In fact, it would be silly to believe that you could, even though noted physicists like William Shatner say "anything is possible". I'll even go so far as to claim that you can't, even though I admittedly don't have a lot of experience, experimental data, or resources to devote to telekinetic orbital mechanics.

Re:Did you even read anything you linked?

[__aaclcg7560]

Use tachyon particles instead and ignore the part that implies that special relatively is wrong.

Re:Did you even read anything you linked?

[michelcolman]

The only faster than light effect that has ever been observed (and has in fact repeatedly been demonstrated), is the situation where a journalist sees the word "entanglement" and immediately starts typing "faster than light communication" without any time delay whatsoever.

In this case, the experiment is about sending entangled photons along a classical channel (interstellar space), using the entanglement to reduce noise a little bit. Those photons still travel at the speed of light, but using a particular quantum trick the error rate can be slightly lower than that achieved by sending non-entangled photons. It's not even a spectacular gain, but I guess every photon counts when you're sending information from a probe that's far away in space.

No faster than light communcation to see here, move along.

Re:test it

[michelcolman]

Actually, what they are doing is sending entangled pairs of photons (both of them) through a classical channel (at the speed of light) and using complicated mathematical quantum tricks to make it slightly more likely for the message to arrive without errors. Apparently, using entangled photons allows a more efficient transmission (less errors) than just using ordinary pairs of photons. But the message still travels at the speed of light.

Forbes blocks ABP, not uBlock Origin

[kunwon1]

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

Re: FTL communciation with entanglement not possib

[michelcolman]

Not to mention superposition.

But if nobody saw them do it, she can be both pregnant and not pregnant at the same time.

Re:FTL communciation with entanglement not possibl

[Gravis Zero]

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?

Entanglement for dummies.

[Fly Swatter]

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 what the other box contains.

Here's where things go off the rails with articles like this. No on has ever claimed they could influence or change the value of one side of the coin such as to change the other half at it's distant location. I would argue the values in quantum entanglement are already set the moment the photons are split apart, and like the coin, they can not be changed by looking at them.

Re:Entanglement for dummies.

[SuricouRaven]

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.

Re:Entanglement for dummies.

[amRadioHed]

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.

Re:Anyone that says 'no'

[Nutria]

I also can't prove that you aren't capable of reaching out with your thoughts, grabbing the Moon, and hurling it into the Sun.

I'm going to steal that, and you can't stop me...

NO MORE FORBES LINKS

[Gravis Zero]

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

Re:NO MORE FORBES LINKS

[ooloorie]

There are browser extensions that get rid of the splash screen. Here is one for Chrome.

Re:NO MORE FORBES LINKS

[BlueCoder]

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.

Re:Anyone that says 'no'

[Fly Swatter]

So shut the fuck up and let the real scientists that get paid to do this stuff figure it out. All of you lack the requisite experience, experimental data, and resources to do otherwise.

But once you know 'it can't be done', to use a phrase from quantum entanglement itself, you will immediately know the grant money 'dried up'.

Just a second, I'll let you know

[goombah99]

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 transport from the past, which is immutable, to the future must be lossy. So you can't send information outside the light cone faster with perfect fidelity. This is not the same as a lossy channel-- which can use error correction to encode perfect transport.

Re:Just a second, I'll let you know

[NotInHere]

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%.

Re:Just a second, I'll let you know

[Black Parrot]

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 travel, unless the mechanism involves swapping the same amount of conserved stuff from the destination.

OTOOH, if there's a conservation of bit values (e.g., # of 0s = # of 1s), several things could get interesting in various ways.

Re:Just a second, I'll let you know

[goombah99]

If you change bits in the past you just erased information.

Another way of saying this is to imagine the limit case. Imagine you were to "write down" the quantum state of the entire universe in the past and try to store that information in the present. The size of your "note" pad would be exactly equal to the size of the universe. That is to store that in the present your would literally have to bit erase the present and over write it with the past's state.

it's equivalent to saying you can't store 2Terrabytes on a 1 gigabyte drive.

therefore to store the past in space smaller than the universe you need to compress the data in a lossy way.

EditorDavid

[110010001000]

EditorDavid: you need to stop accepting submissions from this guy Ethan Siegel. He has links to Forbes that contain MALWARE in the adverstisements.

Re:Did you even read anything you linked?

[fustakrakich]

Violating causality is no joke...

Okay, if it's more than just a speeding ticket, what should the penalty be then?

Possible if the Universe is non-local

[little1973]

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 to be the same in all directions, etc. This was explained before with the Inflation theory, but that one bit the dust (http://www.space.com/28423-cosmic-inflation-signal-space-dust.html).

Re:Did you even read anything you linked?

[SuricouRaven]

Tachyons have never been observed. Even if they can exist, there is no known means to generate them. The only reason to believe such a particle is even possible is that they are a valid solution to certain equations in special relativity.

Re:test it

[unrtst]

When you say use entangled pairs as communication method, it's meaningless gibberish.

Why are so many people commenting like this? Why would you automatically dismiss it?

AFAIK, if you have an entangled pair, move them to distant places, alter one, then read the other, the other shows that change. One problem, AFAIK, is that the act of reading may alter the spin, so you get one bit out of it, and then you're back to nothing - it's not a channel, and the end result is a lot of time to get one bit of info to that destination.

However, if you were to entangle thousands of them, send half of all those to some distant spot, then you could, theoretically, transmit thousands of bits of info, right? There's no going back in time or anything like that, cause it would take however long it takes to travel that distance just to get there - you're just getting the results instantly and one time only (until you run out of your supply of entangled pairs).

Re:FTL communciation with entanglement not possibl

[kheldan]

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 researcher in question over, and then turned out to be completely and totally correct, turning everyone else on their ear, and revolutionizing the field? So quantum entanglement can't be used for FTL communications; so what? The question had to be asked, the answer had to be sought. Doesn't mean it was wasted time, doesn't mean anyone should have their life ruined over it, doesn't mean that someone isn't going to keep looking for ways to create a way of transmitting information faster than light, either. Who needs to be scoffed at, ridiculed, and ostracised, are people who, through peer pressure and mob thinking, seek to prevent science from 'wasting it's time' by exploring seemingly absurd ideas. Every 'failed experiment' is not a failure if there was something learned from it, even if that amounts to 'X doesn't work'. Sometimes, the journey is more important than where it ultimately takes you.

Causality Haiku

[TechyImmigrant]

Before thing comes first
Violate Causality
I now have first post!

Why do you need to know the state?

[pablo_max]

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 of the change like mores code?
I also seems not correct to say it cannot work because we would violate a law. As I understand it, no one has a clue how quantum works. Hell, maybe those little suckers just make a tunnel that connects right through space time to the partner. Who knows!

Re:Why do you need to know the state?

[Athanasius]

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.

Re:Why do you need to know the state?

[Normal_Deviate]

But what if you detect wavefunction collapse? The wavefunction is collapsed by the distant measurement, which forces the local particle to choose its state. And as I understand it, wavefunction collapse *can* be detected, because under some circumstances a wavefunction can interfere with itself, but not if it has been collapsed. For example, with the two-slit experiment, a single photon can interfere with itself and create an interference pattern, but not if it has been forced to choose a slit.

Ergo, the two possible states of the world are: (1) FTL communication is possible; or (2) It is not possible to determine whether a particle has indeterminate state.

Re:Why do you need to know the state?

[Athanasius]

What makes you think that the second particles wave function has collapsed, so far as you're concerned locally, before you force it to by attempting measurement? Entanglement only means that once one of the particles is measured the other when measured will have the complementary value.

Please, honestly, give me a citation from somewhere/one trustworthy about this detection of wave function collapse without the particle interacting such that the entanglement has been destroyed. An repeatable, verifiable experimental result would be ideal.

Re:Why do you need to know the state?

[N3wsByt3]

Hmm. Actually I got a link by a poster here, which is pretty interesting and deals with exactly that:

https://www.sciencedaily.com/r...

Now... the whole thing of me saying it's impossible is based on the assumption that you can't measure a qubit directly without destroying the wavefront. Which, while not a 'law' of physics, was pretty much a core tenet. If that doesn't hold anymore, the principle objection to FTL communication is gone too (I've made another post explaining why, but I'm sure you can see and realise this yourself too).

I too, want to see it repeated and verified first as well, though. :-)

IF it's confirmed, it should be relatively easy to test if it's also applicable and suited for FTL communication. I'm rather sceptical as of yet, but in principle, if the paper is right, I'm forced to re-evaluate my stance on FTL, at least on the grounds that I used (there could be other reasons).

The only thing I find a bit surprising is, if the paper is correct - and it's from 2013 I believe - why no-one has tried out the obvious FTL implications of it. (And if they were successful, I'm sure we'd heard about it).

I find it...unlikely... but not to the same degree as the EM-drive being an actual reactionless drive. ;-)

If you have any thoughts on this matter, feel free to share them.

Re:Why do you need to know the state?

[Normal_Deviate]

My point is that particles behave differently when their state is indeterminate. If this were not true, how would we even know that states can be indeterminate? Could such a crazy idea have been proved, if indeterminate states are observationally indistinguishable from determinate states?

You seem to be suggesting the local particle will pretend to be indeterminate state, even after its state has in fact been determined. I guess that is an experimental question.

Re:Why do you need to know the state?

[Athanasius]

Someone more able to work in the detail of QM should comment.

Off the top of my head: I guess this is saying that if when they measure in this manner the result comes out in a certain way they know the photon still has an un-collapsed wave function? Presumably if it had a definite state it would be either vertically or horizontally polarised ? I'm still not sure that the wave function of the 'second' particle will actually show locally as having collapsed just because the 'first' particle was measured. It's just that when you perform a full measurement you'll get the complementary value.

As you say... where's the experiment to test this? I'm spouting "currently accepted theory in layman's terms", and it's possible that will be proven incorrect.

Re:Why do you need to know the state?

[N3wsByt3]

One of the core tenets was exactly that; that indeterminate states are observationally indistinguishable from determinate states, until it actually got observed, in which case the wavefront collapses in a random way (and thus, no information could be retrieved by it).

However, it seems there is a paper claiming one can measure the (polarisation) state of a qubit without collapsing the wavefront. If this turns out to be true, in principle, it would be possible to get information from the state of that wavefront (to be exact, whether or not it was determined or not - not *how* it was polarised/determined). Logic dictates that, if true, it would be possible to have a set-up where you have several qubits that are originally in an undetermined state, and then you look at each of them if they're still undetermined 10 lightyears away, and create a pattern (and thus info) that way. Even with some random fluctuation in wavefront-collapses, it should be possible to statistically retrieve info out of it.

IF it's true. If not, then it's exactly as I said. And in that case, your last sentence makes no sense, since if the state has been determined, the particle will of course not 'pretend' anymore to be in an indeterminate state. Only, since it's not possible to measure it without determining it (which the paper disputes now), and since the determination is random, it follows no information can be retrieved from it.

Re:Why do you need to know the state?

[N3wsByt3]

Someone more able to work in the detail of QM should comment.

Off the top of my head: I guess this is saying that if when they measure in this manner the result comes out in a certain way they know the photon still has an un-collapsed wave function? Presumably if it had a definite state it would be either vertically or horizontally polarised ? I'm still not sure that the wave function of the 'second' particle will actually show locally as having collapsed just because the 'first' particle was measured. It's just that when you perform a full measurement you'll get the complementary value.

I don't think it actually claims it can measure *what* determined state it is in (what kind of polarisation has taken place). Because in that case, you can't but have a collapsed wavefront, since you actually determined the exact state of the particle itself.

What they're saying is that they can determine *whether* or not a qubit has an undetermined or determined state (without saying anything more about the determined state, thus).

They say they can measure whether it's 'set', or whether it's 'not set', without collapsing it. And, following logic, that alone would be enough to impart some information, indeed. Because if one had 100 individual qubits that are supposed to be in an undetermined state, yet when you measure it at Alpha Centauri (without the wave-function being collapsed), and it would turn out some of them were undetermined, but some aren't anymore (because of polarisation of the entangled qubits deliberately done on Earth), you could create a pattern that sends information. Even if there were random fluctuations individually, you could still filter it out statistically.

IF true, it should be possible, in principle, to have FTL communication. Since that is no small matter, and would earn you a nobel-prize, it's strange to see no paper dealing with this, even after 3 years since its publication...

Re:Why do you need to know the state?

[Tablizer]

Careful, if you hack the universe to find FTL communication, the owners of our universe may just pull the plug on the whole thing.

No...ish...

[Greyfox]

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 measured. I assume this is an optimization technique so the universe only needs to compute the states of the things that someone cares about. Anywhoo, the mechanism by which this information is communicated is unknown (last I checked). I'd guess that they're investigating this mechanism to see if there's something there they can leverage.

Re:No...ish...

[Black Parrot]

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.

not about FTL but about faster data rates

[ooloorie]

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, there are neither experimental nor theoretical results suggesting that it needs to be modified.

Summary

[Vadim Makarov]

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.

Re:test it

[Athanasius]

The problem is that:

1. You don't get to choose which particle of the pair gets which value. It's random as to if it's -1 here and +1 there or vice versa.
2. That's pretty much it. Look up Bell's Theorem https://en.wikipedia.org/wiki/... for a proof that the future-measured state of a given entangled particle isn't pre-determined (no "hidden values"). The only thing you know from a pair being entangled is that whatever value you measure on one particle for the entangled property, you will get the opposite/complementary value on the other particle when it is also measured.

Thus all you can actually transmit using such a system is a random stream of data, with the knowledge that the matching data at the other end is complementary (and thus can be used to derive what you have). Also, this assumes no-one trying to intercept the transmitted particles in the middle. If you don't get your implementation correct it's possible to do so without detection, or for that to be detectable precisely because it broke the entanglement and thus you don't even have a complementary data set.

Re: Did you even read anything you linked?

[KGIII]

I'll bite. I shouldn't but, what the hell? I'm busy elsewhere so I may not even have to deal with any additional derp.

So... If I give you the benefit of doubt, will you actually listen? Science doesn't really work like that. First, you make an observation. Have you observed faster than light communication?

To put it into a bit different light, you aren't supposed to have to prove you're not guilty in a court of law. Not at all. The burden is on the State to prove that you're guilty. It's pretty much like that. Until you have an observation, you have nothing except conjecture. It's nice mental bubble gum but it's sure as hell not science - or even something worthy of formal debate.

Re:Quantum science is in it's infancy

[Athanasius]

There's a difference between "we have no idea how to do this" (heavier than air flight 500 years ago) and "we have a lot of experimental evidence demonstrating that this works in a manner that will absolutely not allow for that" (the current knowledge about quantum mechanics and what it means for entangled pairs of particles).

Re:Remote quantum surveillance

[Athanasius]

No.

Let's assume you have a whole bunch of entangled pairs set up, so that you can consult one per day, month, year, whatever. That still doesn't help. When Twin A checks his particle 1 and sees it has (spin, polarisation, whatever) value +1 all you know is that when Twin B measure their matching particle they'll get value -1. That's it. A did not, and cannot choose that his particle measures as +1 rather than -1. All entanglement means is that the pair of particles will have complementary values measured.

And, no, you can't assign life event, decisions, or any other information to which particle you measure out of the set. Then Twin B would need to measure them all to see... what? Which has changed? No, that doesn't work because the moment you measure any of the entangled particles you lose the entanglement. Measure them all, record the state, measure them all later... oops, now the measurements are no longer correlated with the state of the particles with Twin A. You literally have no idea if Twin A measured any of them without using a (maximally) light-speed conventional connection to ask.

The Internet of the distant future

[WaffleMonster]

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.

Re:The Internet of the distant future

[kuzb]

More like relay stations controlled by a corporate entity.

Re:Quantum entanglement methods for accessing Forb

[Solandri]

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)?

Couldn't read the article...

[fahrbot-bot]

My browser is entangled with an ad-blocker and everything collapsed when Forbes observed it.

Re: Did you even read anything you linked?

[jordanjay29]

What? Since when is science a court of law? New scientific hypotheses aren't assumed to be false before they're proven true, the assumption depends on the experiment and background knowledge (and perhaps the gumption of the experimenter). New scientific theories aren't assumed false before they're proven true, nor are scientific laws assumed to be false before you can point to something and say, 'aha! it is true after all!' To become a theory or law in the first place requires many observations or calculations of an aspect of our universe, and then also ensuring that these results don't come about by some other means.

But all of this is subject to new ideas and new interpretations. It used to be thought true that the atom was the smallest particle in the universe. It used to be thought true that the sun orbited the Earth. It used to be thought true that the species of the Earth were placed here fully formed and evolved to their final states. All of this has been since proven otherwise by later information, but for a time these were scientific truths.

And finally, have you observed the Big Bang? Have you really been unable to know both the speed and position of an electron or are you just not trying hard enough? Observation has never been an absolute necessity for science, calculation and proving the negative are just as much a part of the scientific method as physical observation.

Re:Did you even read anything you linked?

[jordanjay29]

We know they exist, they were the answer to a New York Times crossword puzzle. Or at least, those were the sequence of letters that fit the space and made sense.

Working article link

[evilviper]

This link will work fine even with ad blockers:

http://webcache.googleusercont...

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

Re:So...

[paiute]

He may or may not have fixed your car, and every time the you check you influence the outcome

So... like my real mechanic.

Re:FTL communciation kinda possible

[Theaetetus]

It's not exactly communication per se, but it can be used to indicate instantaneously at a distance which of a predetermined set of actions has been randomly selected.

As to why it's not communication, it's effectively the same as if you had a third party randomly write "attack" or "no attack" on two pieces of paper, seal them up in envelopes, and give them to you and your commander before he left, with instructions to both of you not to open them for 5 years. Heck, once your commander was out of communication range, you could open them at that point, as long as you're willing to be locked into your battle plan.

Re:FTL communciation with entanglement not possibl

[nicoleb_x]

You're assuming that the state has a location. Why can't the state exist in many/any place at the same time? Entanglement may just be the case where a single state is shared.

Re: test it

[tnk1]

The point is that it is *not* a communication technology. You can't communicate with entanglement. Period. You can use it to support something like encryption, however, but the communication needs to come from a different method.

However, if you want to have something that passes through the Earth like it isn't there, you want neutrinos. However, the problem with neutrinos is that being something that barely reacts with the entire mass of the Earth, you're not going to be able to actually detect them on your transmitter either. At least not unless there is some manner of efficiently detecting neutrinos in (relatively) small devices that we are as yet unaware of. As it stands, there are millions of neutrinos that pass through the Earth every second, and probably only like a few hundred of them actually interact with any atom in the entire mass of the planet.

Shatner need to shut up about science

[Anonymous Coward]

Seriously. The guy doesn't know anything about it. It's great that he's enthusiastic, but making statements like "anything is possible" when even to the amateur scientist this is quite clearly not the case is fucking stupid. The man has exactly zero expertise on the subject.

Re:test it

[tnk1]

This could be hugely helpful by lowering errors, thus increasing effective bandwidth. And that could have relatively large incremental benefits. Unfortunately, everyone keeps getting hung up on the FTL possibilities which do not exist.

Re:Quantum science is in it's infancy

[WaffleMonster]

My grandfather did not believe in satellites. Several hundred years ago people did not care about heliocentric model.

Not falsifiable. Just because someone may or may not believe in something has no bearing on merit.

Modern people are so limited, as such they have made a practical simplification to treat speed of light as a constant.

Is there evidence to suggest "c" is not constant?

Quantum delayed choice experiment is a first salvo, a first spin to this oversimplification.

The speed of light is a measure of how fast anything can propagate thru space with the usual laundry list of clarifications and stipulations.

Quantum information does not prorogate thru space.

Somewhere there is a 130+ IQ point scientist and sometime this scientist will come up with another thought experiment, which will later be supported by actual experiment which will provide a different spin, and potentially a breakthrough in quantum mechanic understanding. We just don't know how old that scientist is or even if he or she already born.

There is a legion of geeky nerds who are racking their brains around quantum mechanic phenomena and more experiments more discoveries will expand our knowledge horizon.

There is a legion of geeky nerds who are racking their brains around arranging permanent magnets in a way that creates a free energy generator to power their go carts.

In both cases the math is quite clear on what is and is not possible. It simply does not matter how clever you are.

It is true at any time new evidence can modify understanding about anything. The problem is in the attempt to leverage lack of knowledge as license to support a specific outcome for which no evidence exists. You are of course free to assume anything you want. Don't expect to win any support by simply asserting "we don't know everything".

Re:Remote quantum surveillance

[marciot]

Measure them all, record the state, measure them all later... oops, now the measurements are no longer correlated with the state of the particles with Twin A.

Okay. It wasn't clear from the article that once you measure the particle the entanglement goes away. I had assumed that you could keep measuring the particle over and over again for different outcomes. I had read it as being like a pseudo-random number generator that was set to the same seed when the particles were entangled.

I think my general idea still works, though. I did not say that a twin had any ability to influence what the other saw when he measured his particle. All I assumed is that he could tell what random value his twin had measured by consulting his own particle. If you have an infinite number of particles and an agreed upon sequence of checking them, you could still implement first scenario. You could get the exact same result more easily with the pseudo-random number generator, however, rather than having an infinite bag of entangled particles.

Re:Did you even read anything you linked?

[Black Parrot]

Faster than light communication is impossible and would break the universe as we know it;

General Relativity also broke the world as we knew it.

Ok, cool, but what about that interference picture

[Kartu]

I recall particle "interference" was gone, if particles were detected. Can't one use that with entangled particles?

Re:FTL communciation with entanglement not possibl

[N3wsByt3]

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 collapsing the wavefront). So what I said still stands. But, regardless, it does change the game, agreed. Because they say they can measure whether it's 'set', or whether it's not 'set', without collapsing it.

And, following logic, that alone would be enough to impart some information, indeed. Because if one had 100 individual qubits that are supposed to be in an undetermined state, yet when you measure it at Alpha Centauri (without the wave-function being collapsed), it would turn out some of them were undetermined, but some aren't anymore (because of polarisation of the entangled qubits done on Earth), you could create a pattern that sends information. Even if there were random fluctuations individually, you could still filter it out statistically.

Hmm. Is there any link/paper that handles FTL communication through this particular method? It seems to me, if that article is right, that it would be relatively easy to establish if it actually can be used for FTL communication*. I would have presumed someone would have done it already...(?) If so, I would welcome a link to such a paper.

*Note that the NASA experiment does not do that; as far as I've understood, they just want to maximise the information of photons send to the spacecraft through entanglement. But the information send is still at the speed of light, not FTL.

Re:FTL communciation with entanglement not possibl

[Gravis Zero]

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

Re:FTL communciation with entanglement not possibl

[N3wsByt3]

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 EM-drive, that violates CoE and CoM by simply bouncing microwaves around in itself as a closed compartment, is bullocks. If a microwave-oven (which it is, basically) could violate it that easily, without it leaving normal physics we already know of, then we would already have observed that through myriads of other experiments long ago.

That said, quantum entanglement is less well understood. It doesn't mean 'everything' is possible as some seem to believe, but the boundaries are more unclear. The statement that FTL communication is impossible is only true as far as the wavefunction can not be measured without collapsing it. Which has always thought to be the case, but I just got a link here to a paper which claims it succeeded in measuring a property (namely being polarised or not) without collapsing the wavefront. Which would make FTL communication rather a technical problem rather than breaking any physical law (not that it was defined as such, but it used to be regarded as pretty well established). However, I have little doubt that anything which is a mere *technical* obstacle, humanity can overcome, eventually.

Point is, if that paper is correct and it can be falsified and confirmed, it should be possible to set up a system to see if FTL isn't feasible afterall. Thus, science knows no absolutes, as you say. :-)

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

I've said so for some time now, but...

[dsmatthews9379]

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 discard some pairs and resolve the state of others, with the binary data being encoded in those choices and not in the states of the particles themselves. Consider the following Chain of Entanglement (Q-chain) A[-1-B{-2-]C-3-}D There are relationships between the states of AB BC & CD there is also a correlation between AB & BC so that when we resolve AB we can better guess BC and therefore CD without ever resolving CD directly. If we then select a set of X Q-chains such that we have enough for our guessing to be statistically useful we can discard chain sets that do not have a value that corresponds to the value we wish to transmit.

If I can do something like I have described above I could communicate via a faster than light link.

Re:FTL communciation with entanglement not possibl

[N3wsByt3]

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 for now, but that doesn't change the logic behind it that, if confirmed, the major objection I raised in my particular parent post, has become largely void.

I'm actually not naively endorsing it, nor do I find it extremely likely, and thus I would like to see this paper confirmed by other experiments, especially in an FTL communication set-up, but facts are facts, and IF it would turn out to be true that you can measure a state of a qubit without destroying the wavefront, in principle, you could get information across. It's...well... it's the logical consequence of it, isn't it? Can't help it.

On the other hand, if I were proven wrong and FTL communication were possible, it's actually opening up a lot of possibilities. I'm not one to speculate into fantasies too much, but once you can have instant two-way--communication, it should also be possible, in principle, to, say, have a real-time experience on another planet with a robot-avatar you send to an extra-terrestrial planet before. (presuming you can live enough to wait out the time it needs to get there, so maybe Mars would be a better goal).

Anyway, first things first. I would like to see it confirmed or refuted.

Re:Remote quantum surveillance

[Athanasius]

Technically you would only know, in an FTL sense, that the particle at the other location had the opposite value. Just because you agreed that a certain state of that certain particle would mean a certain action was taken/not taken doesn't mean that the other person didn't change their mind, or wasn't prevented from carrying out the agreed-upon course of action.

You'd still only know if using some light-speed limited communication means to verify the outcome.

Re:Did you even read anything you linked?

[ClickOnThis]

The only faster than light effect that has ever been observed (and has in fact repeatedly been demonstrated), is the situation where a journalist sees the word "entanglement" and immediately starts typing "faster than light communication" without any time delay whatsoever.

Obligatory xkcd.

Re: Did you even read anything you linked?

[ClickOnThis]

You missed KGill's point.

In a court of law, the burden of proof is with the prosecution, not with the accused.

In science, the burden of proof is with the one making the claim, not with the one refuting it based on current knowledge.

And to paraphrase Marcello Truzzi the more extraordinary the claim, the more extraordinary the proof must be.

Denying faster-than-light communication is not an extraordinary claim, because nothing has ever been observed to go faster than light.

Visionary technology

[best shot]

The technology would have to be developed to hold and manipulate the electrons once separated from their entanglement. The absence or presence of a manipulation to the electron would indicate 1 or 0 as in the binary code. There wouldn't be anything transmitted. The faster than light would be only because the other pair of entangled electrons had been incorporated in the communication technology of the space craft before it left Earth. Any manipulation of one electron instantly effects the other. This could be applied to even Earth communication without the need for cell towers or satellite transmission. Now that we have broken out of the mold new ways of perceiving the universe are going to bring us new tools too. We all need hobbies to work on.

I can imagine one simple use

[BlueCoder]

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 short formulas with which it could infer to match the progress we have made in science and technology. Possibly building a better communication system later and get relatively instantaneous results.

Re:You really are a CRETIN!

[brantondaveperson]

Awesome. You should make a website about that.

Re:Remote quantum surveillance

[Athanasius]

I don't think any alien race is going to succeed in entangling all the particles in the Solar System, but even if they do they won't stay entangled for very long. Remember that a lot of the challenges to making viable quantum computers are preventing the entangled particles from interacting with anything else. If they do they're then no longer entangled.

Re:FTL communciation with entanglement not possibl

[N3wsByt3]

Keeping with traditional 'wisdom' of entangled particles (there has been given a link which cast some doubt on this), the reason why what you say doesn't transfer information is as follows:

Say the answer is yes. You open the box with yes. It automatically collapses the wavefront, making the particle determined to a +1 or -1, whatever. You have no control over whether it's +1 or -1, however; it happens fully randomly. So you can't impart info directly that way, agreed?

But, you say, that doesn't matter, since it's the 'yes' box with the qubit that is of importance, and you know that means 'yes'. But... how can the folks back at Earth know? If they open the yes box, they'll see a +1 or a -1. But if they open the no-box, they'll see a +1 or -1 as well. That's because the wavefront collapses in both cases *regardless* of who measured it (you at 20 lightyears, or the folks at home). So the only thing you see, is a +1 or -1 in both boxes, and you can't know if it's there because YOU measured it and caused the wavefront to collapse, or whether it's due to THEIR measurement. In both cases, as soon as anyone measures it, you get a random outcome. And if you don't measure it, you don't know if 'the other side' has changed it or not.

It's the *measuring* that makes it collapse in a random way, whomever observes the state of the qubit. And you can't get the state of the qubit *before* you observed and measured it, and you can't know if it's there because *you* measured it, or *they* did. Basically, the only thing you know is, if you measure a +1, they'll have a -1. But that doesn't help anything in conveying any information, since it's randomly determined.

Now, there's been a link to a paper which claims it is possible to measure whether a qubit is determined or undetermined *without* collapsing the wavefront. Obviously, that would change things. If true. But if not, it's easy to see with my explanation why you wouldn't get any info out of it.

Re:Remote quantum surveillance

[marciot]

I don't think any alien race is going to succeed in entangling all the particles in the Solar System, but even if they do they won't stay entangled for very long. Remember that a lot of the challenges to making viable quantum computers are preventing the entangled particles from interacting with anything else. If they do they're then no longer entangled.

Super-intelligent alien engineers love a challenge and presumably they've had a head start :)

Re:test it

[MillionthMonkey]

Quantum entanglement can result in faster-than-light effects. But not faster than light *communication*. Basically, to decrypt the "message", you have to walk over to the other guy and compare his observations to yours before you can "read" the message he sent.

Long ago proven not to work, so...

[psinet]

..why is this /. news?

99% of readers would have long ago been through this - since quantum non-locality has long been mainstream science.

The simple upshot is that setting a state for a particle in another light-cone, is a long way from sending a message - let alone a sensical one containing information a human could understand.

This "incredible idea to exploit quantum weirdness" is neither incredible nor an exploit as this reader found out in about 1996, in about 2nd year Uni.

Re:Quantum entanglement methods for accessing Forb

[hcs_$reboot]

In Google News you can easily customize the tool to avoid anything coming from Forbes.

Re: You really are a CRETIN!

[Time_Ngler]

Don't cry into your keyboard, you'll short it out that way

neat

[bobmajdakjr]

Just finished mass effect 2 where they described exactly this doing exactly that.

Re:You really are a CRETIN!

[sexconker]

You do not understand entanglement.

Re:Did you even read anything you linked?

[sexconker]

Heisenberg has shown that effect can precede cause at the subatomic level.

No.

Re:Anyone that says 'no'

[sexconker]

Wake me when you decide to post anything worth reading.

Re:FTL communciation with entanglement not possibl

[kheldan]

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.

Betteridge's law of headlines

[luis_a_espinal]

NO.

Re:FTL communciation with entanglement not possibl

[N3wsByt3]

While true, it still sheds some doubts on my former absolute stance it wasn't possible, I regret to say.

Let's say you can perform weak measurements with some uncertainty, without it collapsing the wavefront.

As long as that uncertainty is lower than the statistical chance it being equal to a random number (aka, 50%), it would still mean one could get information out of it in a statistical way.

Let's say you have two qubits, the right one mean yes, the left one no. If you can check both qubits without collapsing them, and you note that the first (yes) is more likely to be in a determined state than it is to be in an undetermined state (this would be the 'some uncertainty' you spoke of), then you would be 'more close' to the answer being yes than no. And, if you would have 10 pairs of those, and it almost always showed the right qubit to be in a determined state, it would augment the statistical certainty that the message is 'yes'.

While the amount of information you would get from it is indeed limited, it would still mean you can get *some* information from it. In that case, how meagre it may be, you would have information at FTL.

Well, that's what I think of it, reading that paper. Feel free to point out any mistakes in my reasoning.

Re:FTL communciation with entanglement not possibl

[N3wsByt3]

Well... let' say I *could* be wrong. ;-)

you're right that the entangled pair stays undetermined on itself, but, as far as I can see, this doesn't stop the possibility of retrieving info.

As I interpreted the paper, what they're saying is that they can determine if the wavefunction has collapsed or not, without it actually make it collapse by doing so.

In that case, let's say I have 100 qubits, 50 times 2 qubits. You agree before you leave Earth, that they'll all stay in the uncollapsed state, unless you want to say something, and what you're going to say is agreed on in front. For instance, if the first one is collapsed, it means 'A' and it means you must send a probe into the star A, if the second one has collapsed, it means 'B', and you have to send a probe into star B. Now you measure the qubits in the way the paper describes. You look at the first pair; you see it indicates the first qubit is in a determined state, and the second isn't. You look at the second pair; you see it indicates the first qubit is in a determined state, and the second isn't. You look at the third pair; idem. You look at all 50 of them, and the vast majority of them indicate the first qubit is in a determined state. Then it's pretty sure Earth send 'go for the first star A', no?

It doesn't say in what polarisation-state qubit A is in, exactly, but you don't need to know that. Only that it indicates that it's collapsed.

So..what am I missing here? If the paper is right. If. Wouldn't that mean you *can* retrieve info this way?

You are right that a weak measurement doesn't influence the outcome of the state it is in, but nothing prohibits the folks *on Earth* to do a strong measurement, thereby collapsing the wavefront, and the guys at Alpha Centaury to measure it in a weak way, thereby identifying the first qubit has collapsed.

No?

Re:You really are a CRETIN!

[michelcolman]

That's not how entanglement works. In your example, with entangled photons being sent from halfway between A and B, all A and B can do is measure their particles and then, afterwards, find out that their measurements matched. Neither A nor B can choose which information to send.

It can be proven that both particles really were in a superposition of states until they were measured, and they did not contain any hidden variables that would determine the outcome, so the "information" of what state the particles ended up in had to travel faster than light from one to the other, but A and B have no control whatsoever over this information. All they can do is compare their measurements and find that they somehow ended up matching.

If someone ever did find out how to transmit actual, usable information faster than light in any way, that would automatically mean that it would also be possible to send information back in time. Things that are simultaneous for some observer are actually not simultaneous at all for a different observer who has a different speed (as has been proven with GPS satellites). So something that travels "instantaneously" for one observer, is actually traveling back in time from another point of view. Repeat this back and forth to send information back in time to the same location, allowing you to get tomorrow's stock quotes, or possibly hiring a hit man to kill you before you could send the message you hired him with.

Now, with parallel universes this could still work without contradictions (you might get a message from one universe but end up living in another universe where things are completely different) but it certainly is not as problem free and straightforward as you make it seem.

Trust me, people are not just saying FTL is impossible because they are narrow minded. Scientists that are much smarter than you have thought about this a lot longer and harder than you. That does not mean that they cannot possibly be wrong, but you certainly ought to educate yourself on the subject before dismissing their hard work like that. It's not as simple as you think.

Re: Did you even read anything you linked?

[N3wsByt3]

I think the point is, one making the *original* claim is the one that needs to provide proof.

Thing that lack any way of observation, are scientifically worthless. Maybe they exist, maybe not. But you can't say anything sensible about it.

Next!

If you postulate 'God', thus, it's for you to prove God exists. If you can't prove that, saying 'but you can't proof he doesn't' is besides the point. In the best case, it just means it should be ignored, just as the postulate 'tooth fairies exist', and 'magical dragons exist'. Maybe they do, and maybe they don't, but since you have no way to know, the complete concept is worthless in a scientific context.

In practise, of course, since one has to have some pragmatism at least, we consider it 'not true' or 'non-existent'. That's, strictly speaking, not a purely scientific stance, but it is one that is de facto the most sensible. With a limited budget, personnel and time, you can't expect the scientific community to research every crack-pot idea and extremely unlikely idea or concept out there, certainly when that has no observational nor theoretical basis, after all. It's a matter of gradation, thus, and the lower you get on that scale (and without any theoretical substantiation, nor observational proof, you're scoring extremely low) the less likely it's to be considered worthwhile. 'Impossible' in that sense, just means: so extremely unlikely and doubtful that one is best of ignoring it altogether.

Re: Did you even read anything you linked?

[david_thornley]

The burden of proof is on the one making a definite statement. If OP had said that FTL communication was possible, the burden of proof would be on OP. OP, however, seems to have assumed it might be possible, and that doesn't require proof. The statement that it's impossible is a definite statement, and requires proof. Moreover, it's a statement about both what we know and what we don't know, and that is not an ordinary claim. We know physics is incomplete, and we really don't know what we'll find.

We can say there's no way to do FTL compatible with known physics. We can say that we can't have FTL communication and Special Relativity without being able to communicate into the past.

Re:test it

[david_thornley]

AFAIK, if you have an entangled pair, move them to distant places, alter one, then read the other, the other shows that change.

No. If you alter one, that breaks the entanglement. Suppose we're sending entangled particles with one of each pair having spin up, and one having spin down. If I measure a particle, I know what the person with the other particle will measure with the entangled particle (provided that person does the same measurement with the same orientation). If I affect the spin of a particle, it doesn't do anything to the entangled particle, because it breaks entanglement.

Re:Anyone that says 'no'

[david_thornley]

Theories are concrete. If they weren't, they'd be conjectures or something else. Theories aren't proof, but neither is anything else in science. A law of science is nothing more than a theory that everybody is convinced is true.

We can't prove FTL communication is impossible, although that's very strongly the way to bet. We can prove that quantum entanglement in any form that agrees with current theories does not allow FTL communication.

Re:Did you even read anything you linked?

[micahraleigh]

Causality can't be scientifically proven in any test.

Time indexes only have relations to each other because agents decide to view them that way.

Only two (subjective) time frames are real: the instant and eternity.

See B Theory of Time, Sartre, Kierkegaard, etc.

Re:Remote quantum surveillance

[david_thornley]

If we have an entangled pair, we know that the two particles will have opposite readings (in a very simplistic sense, but this description works for proposed FTL communication), so it'll be random. We also know that changing whatever the reading measures breaks entanglement. Therefore, our alien race will know what shape the Earth was in when they left, because of the entangled particles, but they really could just have made notes instead. They won't know what happens when the state of any particle on Earth changes.

Re:Remote quantum surveillance

[marciot]

Therefore, our alien race will know what shape the Earth was in when they left, because of the entangled particles, but they really could just have made notes instead. They won't know what happens when the state of any particle on Earth changes.

Thanks for clarifying. Seems like entanglement is much less useful feature of the universe than I had expected. Is it good for anything?

GA on QP?

[Tablizer]

What if someone creates a quantum physics emulator, and then runs genetic algorithms against it to find a useful way to communicate faster than light?

Just because no human has figured it out doesn't mean it isn't possible. Maybe with enough analytical power, AI can find a solution. There may be a round-about path that nobody has spotted yet.

I suppose one problem with this is that there has to be some intermediate "success" to provide feedback to the GA system in order to evolve against. If it's all-or-nothing, it will probably get stuck at "nothing". Communicating the state of the entangled partner is one possible intermediate success, but is there anything between that and "real" communication?

Re:Anyone that says 'no'

[Khyber]

Wake me when you actually work with quantum particles (like photons) and study their effects both quantum and classical.

I have the feeling I'll be asleep and waiting a long time for you to catch up.

Re:Anyone that says 'no'

[Khyber]

Well, if we're going to go there, then Moore's Law basically is bullshit, and needs to be immediately downgraded to conjecture.

Re:You really are a CRETIN!

[misaltas]

If someone ever did find out how to transmit actual, usable information faster than light in any way, that would automatically mean that it would also be possible to send information back in time.

No! No! Ugh. No! Even if you could send a controlled bit of information from A to B faster-than-light using two entangled particles, all that means is that bit of info traveled from A to B quicker than it would have if it were traveling the speed of light. Nothing about this scenario sends anything back in time. If you assume that information you're receiving is traveling the speed of light, it might appear to be coming from the future, but it's only coming from the same time in someone else's reference frame.

Example:

An observer on a 155ly-distant planet with kick ass telescope is watching Ft Sumter about to be attacked. If the observer and Gen Beauregard possess a pair of entangled particles, (even if you could control the bit, which you can't) no instantaneous controlled bit of information can reach the general informing him that attacking Ft Sumter will eventually be a bad idea. Even to this telescope owner, the general is long dead and the battle long over. The information that was instantaneously sent from the observer today (in their frame) reached us today (in our frame). The light hitting the telescope today left Ft Sumter 155 years ago. Even in the observer's reference frame it was 155 years ago.

Re:Anyone that says 'no'

[sexconker]

QQ babby no unnerstand kwantum intengomans

Re:You really are a CRETIN!

[michelcolman]

Look up relativity of simultaneity. I'm not talking about perceived simultaneity (observation) but actual simultaneity corrected for propagation delay. If two events are simultaneous for one observer (after correcting for propagation delay), a different observer with a different speed will disagree. There is no objective way of defining simultaneity. This can be exploited by sending a message back and forth using different frames of reference to really send it back in time.

Re:You really are a CRETIN!

[michelcolman]

At least it could if FTL transmission were possible.

Re:Did you even read anything you linked?

[painandgreed]

Tachyons have never been observed. Even if they can exist, there is no known means to generate them. The only reason to believe such a particle is even possible is that they are a valid solution to certain equations in special relativity.

The only thing I've really heard reading physics books that lead me to believe their was some actual science behind it was an off hand mention in a Michael Kaku book that somebody showed that they could exist and probably did in the early universe, but hopefully can't any more because it would indicate the universe was at a false vacuum, and they would eventually cause instability to make it go to a more stable state (and changing the laws of physics and probably destroying/recreating the universe in the process).

Re:Remote quantum surveillance

[david_thornley]

It's potentially useful in secret communications, provided we can keep the entanglement reliably going across useful distances. Send a bunch of entangled particles, perhaps to share a random number (like a 256-bit AES key). Do this in a previously agreed-on way (if looking at spin up or down, tilt the detector at an angle, say). The sender measures the entangled particles at one end, the receiver at the other. If all is well, they match, which can be confirmed with a quick innocuous message back. If the sender can read that message, it shows that it was not intercepted and read en route, as there is no way for somebody in between to read the key and send it on intact.

Re:Anyone that says 'no'

[david_thornley]

Moore's Law has been either a good prediction or a self-fulfilling prophecy.

Re:Did you even read anything you linked?

[SuricouRaven]

They are consistent with relativity, mathematically. You can't accelerate anything up to the speed of light, but the maths doesn't stop you creating a particle already exceeding it. They would be very strange particles indeed - they would have imaginary mass, something never observed, and allow for causality violations, also never observed. So they might exist, but it's unlikely: They are not consistent with observations. If they can exist it would have to be under conditions so extreme that they have never been experimentally observed, like the early universe.

Re:FTL communciation with entanglement not possibl

[RespekMyAthorati]

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

But according to the article, Captain Kirk says it would! So that's that.

Re:FTL communciation with entanglement not possibl

[N3wsByt3]

then it must be so! ;-)

My only regret is, that Mr. Spock can't say that anymore.. :-(