European Researchers Propose Quantum Network Between Earth and ISS 209
New kalalau_kane writes with this tidbit from Extreme Tech: "A group of European researchers has proposed the largest quantum network yet: Between Earth and the International Space Station. Such a network would see entangled photons transmitted over a distance of 250 miles — two or three times greater than previous quantum communication experiments. Not only will this be the first quantum experiment in space, but it will allow the scientists to see if entanglement really is instantaneous over long distances, and whether it's affected by gravity."
The proposal (licensed CC BY).
10,000 times faster than the speed of light? (Score:5, Interesting)
I don't get it. I thought it was instantaneous and that number is just a crap number based on distance.
Re:10,000 times faster than the speed of light? (Score:4, Informative)
actually it comes from this article:
http://www.extremetech.com/extreme/150207-chinese-physicists-measure-speed-of-einsteins-spooky-action-at-a-distance-at-least-10000-times-faster-than-light [extremetech.com]
Not faster than light (Score:5, Insightful)
Re:10,000 times faster than the speed of light? (Score:5, Insightful)
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Given that according to SR there is no such thing as simultaneity at two different locations in space, how can you tell it was instantaneous?
Re:10,000 times faster than the speed of light? (Score:4, Informative)
>It is instantaneous
Correction: current theory postulates that it is instantaneous, but theory can only be known to be accurate to within the limit of our measuring devices, so "at least 10,000 times faster than light" is the more accurate statement. The whole point of the ISS experiment will be to see if the addition of more potentially confounding factors causes the measured reality to depart from the predicted behavior.
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No (Score:3)
This is bullshit. The scientific content behind this claim is that "nonlocal realistic models that reproduce the results of quantum mechanics must have speed of communication at least 10,000 faster than the speed of light in some arbitrary ference frame that we've chosen".
This means that this number is completely irrelevant, i.e., does not measure anyhting related to the real world.
What can be said, scientifically, about the speed of this channel is that it is the speed of light, because we can only actuall
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What can be said, scientifically, about the speed of this channel is that it is the speed of light, because we can only actually measure the presence of the information on the other side after a light signal is sent from one party to the other.
The fact that it looks instantaneous is more of an artifact of our mathematical formalism, and a common philosophical misunderstanding about the nature of the quantum state (i.e., people regard it as objective rather than subjective).
That doesn't follow. You can only confirm the measurements agree after a speed of light delay, but you can perform the measurements at very close to the same time (the 10000x speed of light number is just the resolution of the clocks that confirm when the measurements were taken).
And WTF is "subjective vs objective" about the spin of a particle? Sure, the word "spin" is arbitrary (likely nothing is actually spinning), but it's an objectively measurable property just like charge or mass.
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Basically it is impossible to prove instantaneous travel because our most sensitive instruments will only go down to a certain value. Our most sensitive measurements demonstrate a minimum of 10k times speed of light. If our instruments become 10 times more accurate then they will likely be able to say that it is a minimum of 100k. Translation, error correcting and processing time have nothing to do with it.
Only 250 miles to the ISS (Score:3)
Re:Only 250 miles to the ISS (Score:5, Interesting)
I doubt the extra 400km you get from doing it on the ISS is the point, because picking two points on the earth's surface that are opposite each other would be 12740km apart so the extra 3% is hardly significant.
Probably of more interest is that the ISS is doing an average speed of around 27,800 km/h which is sufficient for relativistic effects to noticeably come into play. In addition the ISS is in a different frame of reference to anything on the ground. These factors are much more interesting than the extra distance.
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Also, different curvature.
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average speed of around 27,800 km/h which is sufficient for relativistic effects to noticeably come into play
not really...
27,724 kph = 7.7 kps = 2.5688 e-5 c = fast, but not relativistic fast which is more like 0.1 c.
Re:Only 250 miles to the ISS (Score:4, Interesting)
it is fast enough that they can notice the difference in very accurate clocks...thus it is relativistic
for example GPS Satellites loses about 7 microseconds a day [ohio-state.edu] due to relativistic effects.
Oooh gravity experiment (Score:5, Interesting)
Re:Oooh gravity experiment (Score:4, Insightful)
wrong, it is actual science and the way things behave, and the equations are complete (outside of realm of heavy space-time curvature such as near black hole). It is just different from the mental model most humans have. Nothing stopping anyone from taking prerequisite basic calculus and then basic quantum mechanics course.
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Well saying they are complete is wrong. Both General Relativity and the Standard Model are correct within experimental error within the tested limits, which does leave very little wiggle room. However they are not complete and very unlikely to be complete even in regions of normal space-time curvature.
It would be like saying Newtonian Mechanics was complete at the beginning of the 20th Century. Sure within experimental error at the time it appeared complete. However we now know that it was not. A combinatio
QM is complete? Really? (Score:3)
Not quite true. The equations appear to be complete - i.e. they appear accurate to within the limits of current experimental error; however, assuming we're not living in The Matrix, the equations are only a mathematical model of a physical reality that we still have very little understanding of, hence the various superstring, etc. theories that seek to explain the equations. Prediction is only half of what science strives for, and the understanding still eludes us.
Moreover, there are theoretical inconsist
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So they appear complete by all known methods, but you insist that they aren't without any evidences or maths? how cute.
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No. We KNOW they are incomplete because they cannot be reconciled with relativity which we have also tested. That means that there is necessarily something missing.
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You affect one, the other reacts without a particle or wave traveling between them,
And there is the absolute proof that you don't understand anything about quantum entanglement. You do not affect one in the slightest. You are only measuring the state of one the member pairs. You are not setting any kind of state, and attempting to do so would break the entanglement.
You have thrown out a lot of insults, and then when asked to provide links to your purported NASA information refuse to do so. Fact is, you hav
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"It's a quantum thing! You wouldn't understand!"
I think it's more like, "It's a quantum thing! Nobody understands!". Yes, we have equations that balance, but to my knowledge there's no mechanism explaining simultaneous action separated by light years.
I have my money on that separation being merely illusory - that the two particles aren't actually two, but just how we perceive the mapping of reality onto (or into) 4D spacetime, but that's just my speculation.
Always a letdown. (Score:2)
Re:Always a letdown. (Score:5, Funny)
Can someone please explain to me why this can't be used for instantaneous communication purposes?
QE is rather like being married. You know that whatever you decide, your partner will want to do the opposite. However, no actual communication is involved.
Re:Always a letdown. (Score:5, Informative)
Basic explanation. So I have two entangled particles, and we move them apart so you have one and I have one. At this point we have no idea what the spin on either of them is, in fact it is not determined till we try and measure it, but they must be different. I now measure the spin on mine and find it is +1, meaning yours is -1 "instantly". You can now measure the spin on yours to confirm that.
The problem is because the spin of the particle is undetermined until I read it and when I do read it the result will be random, there is no way to transmit any useful information.
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you can transmit your finding to the other person, at equal or less than lightspeed, so they don't have to measure theirs. BUT they won't get that information instantly, so the whole thing is useless for FTL comm. What is can be useful for is secure communications as "reading" one of two or more entangled particles affects the state of them all.
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So, you can't control the spin on either particle?
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So they are two particles that are are in sync with each other. So the information doesn't travel faster then light, it is just implied.
So if we try to change the spin in a meaningful way we would break the sync thus they will no longer be entangled?
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So they are two particles that are are in sync with each other. So the information doesn't travel faster then light, it is just implied.
Not quite, but the reasoning is subtle. Say you have 2 spin-entangled particles, such that the spins must be opposites. You have to pick an angle to measure spin (up or down). If the same angle is used for measuring both particles, the results will always be 100% correlated (one up, one down).
However, if the measurements are taken at different angles, the results will be somewhat random. If the measurements are at 90 degrees to one another, the results will be 0% correlated. If the measurements are at
Re:Always a letdown. (Score:5, Informative)
Not yet. anyway. Someone will borrow another sci fi concept and magically make it work.
No they won't. There is a certain cult that treats science as a religion and refuses to understand that there are basic laws of physics that constrain us. FTL communication causes a litany of paradoxes and trying to turn quantum entanglement into a FTL communication device shows a fundamental lack of understanding of what is going on.
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Do you thoroughly investigate every claim about perpetual motion machines and hope that some day, someone will figure out how to circumvent the laws of thermodynamics?
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Jackpot! This is the whole issue. Just observing these correlations means nothing, as you said, the same data comes out of our friends with the cards.
But the reason we are fascinated by entanglement is that there is more to it. We can actually prove that no theory in which the contents of the letters were predetermined (and FTL communication does not exist) can reproduce the correlations that can be produced via entangled states. This is the famous Bell's theorem [wikipedia.org].
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Up to the point you describe, the classical (a pair of cards with different colors) and quantum (a pair of photons with different polarizations) systems behave the same. However, there are some nifty features of the quantum system that can't happen classically. For example, you can rotate the polarization of one entangled photon (without knowing what it is) --- then, measure both photons, and they'll still be in opposite polarizations, even if you carried out the polarization rotation and measurement so far
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If we can influence them to rotate, can we influence them to not rotate as well? Because if that were the case, we would have the basic for a 2 bit communication system.
For example: measure the receiving end at 1 second intervals. Three rotations = start of message. From there, rotate = 1 and no rotate = 0. Rinse, repeat.
I would imagine that the reason we don't have this is because we can't influence them not to rotate.
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Doesn't work --- on the receiving end, you have no way to tell whether or not the bit was rotated on the opposite side. You see a random bit; suppose it's a 1. There's no way to tell whether this was a 0 "to start with" then rotated, or a 1 "unrotated." The original states of the bits are random: you can't produce entangled bits knowing that one side starts with all 1's, and the other starts with all 0's.
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Even in the classic universe groups of 'things' can have properties that can change at FTL speeds but they like "spooky action at a distance" effects with entangled photons can't transmit information FTL.
For example in Maxwell equations
Induced polarization current P has no constraints about speed.
http://arxiv.org/pdf/physics/0405062v1.pdf [arxiv.org]
http://www.iasf-roma.inaf.it/congress/public_html/Congress/Ardavan%20Rome.pdf [iasf-roma.inaf.it]
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Another example of "classical superluminal" properties is sweeping a laser pointer across a distant wall: there's no classical physical law which prevents you from rotating a laser pointer so the point of light on a distant wall moves from point A to B "faster than the speed of light." In this case also, there's no way to transmit information from A to B faster than light via this method. Your linked paper is a clever fancier version of this --- setting up "extended systems," so it appears that a polarizat
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Nope. You can't tell on the receiving end whether or not the bit you're measuring was or was not rotated. A measured '1' could be a 'rotated 0' or an 'unrotated 1', so you know absolutely nothing about what the message sender is doing (only that, if she measured her bits right after you measured yours, she'd see the opposite values).
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Your ISS partner doesn't have a '1' filter. They have an "all 1's become zeros, all 0's become 1's" filter. In both cases, you just see a random stream of zeros and ones. As soon as your ISS partner "looks" at a bit to tell whether its a 0 or 1 (e.g., if they want to apply a filter only to the 1's), they break the entanglement on that bit --- after that point, they can flip the bit all they want and it does nothing on your end (you just see the random bit that's opposite of whatever they measured at the poi
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See here [slashdot.org] for amore detailed answer. The difference is subtle.
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The problem in your scheme is "set one set of pairs to some value": you can't do that. Quantum mechanics forbids you from setting one side of the pair to values you want (without first breaking the entanglement, so the other side won't see the results).
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Information is basically the "minimum" stuff that needs to be sent to have "causality". For example, I can cause you to be or not be punched in the face by either walking over and punching you in the face or not; but that requires a lot of work on my side. What's the "minimum" I have to do? Well, perhaps you're already sitting in front of a face-punching machine. All I need to be able to do to have "causal" impact on your face is send some "information" to the face-puncher machine; a tiny electrical pulse t
Re:Always a letdown. (Score:4, Insightful)
Can someone please explain to me why this can't be used for instantaneous communication purposes?
Because that would require FTL transfer of energy/information.
It's like if three people were in a room and #3 put a nickle in #1's pocket and a dime in #2's pocket completely randomly. They all know there is only the possibility of a nickle or a dime but 1&2 won't know what coin until they actually look in the pocket.
#1 flies to Mars on a rocket.
#2 stays on earth and looks in his pocket. He now knows instantaneously the value of the coin in #1's pocket on Mars.
Re:Always a letdown. (Score:5, Interesting)
Because the universe doesn't seem to like causation violation, so all its operating principles preclude faster-than-light (which, in Einsteinian relativity, is equivalent to "faster-than-causality") information transmission.
A rough "classical" analogy for quantum entanglement is: seal two cards, one white and one black, in a pair of envelopes. Shuffle the envelopes, and give one to a person who travels to the Moon. Whenever they open their envelope, they'll instantaneously know what the other envelope contains. However, this doesn't instantaneously "transmit" any information: all the information was "transmitted" when the person carried their envelope to the moon, at under the speed of light.
The "quantum" part of Quantum Entanglement adds some fun not-in-classical-physics features to this analogy. For example, you can make a machine that will flip a black card to white and white to black (without telling you which); when the person on the moon puts their envelope through such a device, it can still stay "in sync" with the other envelope (when they are both opened afterwards, they'll still have opposite-colored cards). However, no information is transmitted: the Earth person has no way of knowing (unless you tell them through speed-of-light-or-slower channels) whether or not the Moon person has used the card-flipping machine; once they've checked their own envelope, the entanglement is broken and changing the Moon envelope's contents no longer changes the one on Earth.
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Because the universe doesn't seem to like causation violation, so all its operating principles preclude faster-than-light (which, in Einsteinian relativity, is equivalent to "faster-than-causality") information transmission.
I take issue with that somewhat: as I understand it, FTL communication will only interfere with causality in highly contrived circumstances, where the endpoints of the communication are moving at relativistic speed relative to one another. An ansible that would break if the distance between the endpoints changed rapidly would protect causality.
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FTL communication interferes with causality (within Einsteinian relativity, which so far seems to be a pretty solid theory) because if you have something that looks like FTL communication in one reference frame (a signal is sent from spacetime point A which arrives 1 year later at spacetime point B, which is 2 light years away from A), then there exists some other frame in which causality is violated: B receives the signal *before* A sends it (in this case, there's another frame where A and B are at the *sa
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Sorry, stupid slip-up (need more coffee!) --- there's no reference frame where A and B are at the same location and reverse time order. However, you can pass through a frame where A and B are closer together and at the same time, to where A and B are further apart but in reverse time order (which you can't do for points that are closer in space than in time in any frame): FTL communications forwards-in-time would also allow communications backwards-in-time if the sending/receiving devices where thrown at th
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You may consider the circumstances "contrived" in the sense that you need huge velocity differences between the frame in which A precedes B, and that in which B precedes A
More than that: as I understand it (and it's been a while), it's not enough for some third reference frame (neither A nor B, but some observer) to be moving fast relative to A/B to get a paradox. You actually need A moving fast relative to B to get a paradox. Therefore, a mechanism for FTL communication which cannot work (not a matter of how good your engineers are) if A is moving fast relative to B protects causality.
For example, if keeping a wormhole open required power dependent on the relative speed o
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I know the analogy, but I always wondered how you can tell your switching-machine works, if you are not allowed to check.
As far as I can tell, the result of checking is random and it is still random after the machine 'switched' something. So nothing really happened.
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In a sense, you can't "tell" the switching machine works on particles you aren't allowed to measure on both sides --- for the same reason that you can't "tell" there isn't a giraffe that appears in your closet whenever the door is closed and you can't look. However, the switching machine can be one that's proven to work whenever you pass a known-state particle through (just like you can prove there's no giraffe in every instance that you open the closet door); you can make a polarization rotator that works
Quantum-entanglement deniers? (Score:3)
Wow - a dozen or so messages and not yet one from quantum-entanglement (QE) deniers.
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What is quantum entanglement denial? I mean, I understand people will believe lots science to be false for a ton of stupid reasons, but I haven't heard of this one. Could you explain their position?
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I don't know what particular form of QE denial DavidHumus has run across, but what I've seen usually (like most denialisms) starts with some critical misunderstanding of QE: e.g "QE lets you transmit information faster than the speed of light"; then concludes "you can't transmit information faster than c, thus QE is bunk!".
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Quantum particles do not become "entangled" so that one entangled particle's spin magically becomes the opposite of the measured entangled particle's spin. The US Government has a secret program in charge of flipping the spins of quantum particles in order to make them appear entangled in order to benefit the rich and powerful.
Wake up, sheeple!
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Talk about a quantum mistake.
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Well, QE deniers still have a leg to stand on. The experiments so far aren't quite conclusive yet. But since all the evidence thus far points to QE and not intuition, it's likely only a matter of time and experiments like this one until that door is shut.
Quantum Entanglement Does Not Transmit Info (Score:3)
No, the article isn't suggesting this, but every time quantum entanglement gets brought up on Slashdot, someone suggests how we can use it to communicate FTL. Quantum entanglement is the equivalent of instantaneously sending a random message (more complicate than that, really). No information is actually transmitted. The first time I tried to wrap my head around Quantum Entanglement, I thought it could be used to communicate to far-away places (even other planets) with no latency, but as I understood more, my hopes were dashed.
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Care to post a link?
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Perhaps there was a Slashdot article with a lousy summary (shocking!) that mislead uninformed people into thinking NASA had a method for transmitting data between entangled particles, but NASA does not have a method for transmitting data between entangled particles.
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Heh, many years ago I actually designed the theory for a FTL communication channel - all I needed was a way to use N remotely entangled particles to generate N+1 of them (or a serious boatload of particles to start with). The essential element being that, while random, the probability distribution can in fact be manipulated. It makes for a very "noisy" transmission medium, but with enough redundant bandwidth it should be possible to get a message through.
But then despite multiple attempts I've yet to unde
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Here's how FTL communication can break causality.
In your reference frame, spacetime points A and B are 2 light years apart, with B "happening" 1 year after A.
A sends an FTL message to B (arriving 2 light years away, but 1 year later).
Here's where relativity messes you up: by changing your reference frame, you can trade off between the "space" and "time" differences between A and B, so long as the "invariant interval" s^2 =(space difference)^2 - c^2*(time difference)^2 remains constant, and continuously conn
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Heh, many years ago I actually designed the theory for a FTL communication channel - all I needed was a way to use N remotely entangled particles to generate N+1 of them (or a serious boatload of particles to start with). The essential element being that, while random, the probability distribution can in fact be manipulated. It makes for a very "noisy" transmission medium, but with enough redundant bandwidth it should be possible to get a message through.
Essentially your design boils down to "I have a proce
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Not true - it's possible to manipulate the probabilities of quantum states without collapsing them, in fact that's what much of quantum computing involves itself with. And if I can shift the probability of measuring a given spin from 50:50 to even 51:49 then, given enough data points, that shift can be detected in the entangled particles. In reality it's easy to shift the probabilities much farther than that, though most of the naive techniques involve repeated collapsing of the quantum state which would
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The problem is your forms of manipulation on the "non-entangled" partner don't "transmit" to the entangled partner --- no matter what you do, it'll still be 50/50. To the extent that you "partly" measure the polarization and gently tweak the distribution of particles on your end, you also "partly" break the entanglement: there is no longer 100% correlation. The more you "coerce" your particles into a better-known state, the weaker the entanglement correlation becomes, in proportion such that you *never* get
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Wouldn't it be more accurate to say there is zero corresponding change not "a small change in probability"? As long as it is non-zero there is some information transmitted and this clearly isn't the case.
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Quantum entanglement involves measuring current state not manipulating current state. If I manipulate either entity in the pair, I have broken entanglement. Yeah, I wish it weren't true either, but it is what it is.
Largest quantum? (Score:2)
Cognitive dissonance at its finest!
at least the 5th story in a row (Score:2)
Let's see, how many times do you think I have to copy and
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You still think you can transmit data faster than light. How cute.
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I am a professional physicist. Entanglement does indeed appear to be "instantaneous over long distances". However, no data is transmitted through this process. You're half-right, half-wrong: right on the part most people don't argue against, and entirely wrong on the important question of data transmission. And you're all wrong on thinking you're in any way qualified to comment on this question, because you're obviously not.
Simulation (Score:2)
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Since "the universe as simulation" is an un-disprovable proposition that could be made regardless of what we observe (really, what would indicate a non-simulated universe? flaming letters in the sky saying "THIS IS NOT A TEST"?), folks use all sorts of "evidence" to support it (especially "wacky" quantum concepts poorly understood by the general public and some metaphysical philosophers). This doesn't prove the universe isn't a simulation, either; only that, so long as the proposition remains untestable (we
This is great (Score:2)
But really, we can't find some better form of energy? We can soon instantly transmit data faster than light across hundreds of miles yet still need to explode dinosaur juice to make our mechanical wagons move?
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" instantly transmit data "
No information will be transferred instantaneously.
And why are you trying to compare apples to the sqr root of -1?
FTL communcation with a stick (Score:5, Funny)
2. Push the stick from one end and it moves at the same time on the other end for instantaneous FTL communication.
3. Sell sticks to day traders.
4. Profit.
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Re:Not Much Advantage Gained (Score:4, Insightful)
Presumably, the ability to shoot a beam of light >250 miles, without needing to build a 250-mile-long evacuated beamline, is a major advantage gained. The Earth is surrounded by this annoying thing called "the atmosphere," which wreaks havoc with light traveling only a few miles; the faster you can get out of the atmosphere (by, e.g., shooting straight up), the easier it'll be to get any useful amount of light to the other end.
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Perhaps, but the ISS is only ~5% farther from the center of the Earth than sea level, so that's only a ~10% difference. Seems like gravity would have to have a huge effect on quantum entanglement for that to matter.
Re:Not Much Advantage Gained (Score:4, Interesting)
Depending on the experiment, 10% differences can be pretty obvious to measure. With the best atomic clocks, we can now see relativistic effects due to gravitational potential differences corresponding to 1m height change in the lab. Without understanding the experiment, you have no way to judge whether 10% differences are negligible or whoppingly huge compared to experimental sensitivity.
Re:Entangled Photons? (Score:5, Funny)
Very few scientific advances have been made without a few Unforeseen Consequences, but that's no reason for Apprehension or Questionable Ethics so we may just need to Forget About Freeman.
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When the hell are we going to get HL3?? I don't even ask for that much, a new HL2 episode would be nice!
(pardon moi a bit of internet rage just in case some valve guy is actually reading this)
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Ou need to understand Valve counting.
1
2
new game.
Or
Excited about new game
perfecting the game in the sequal
3 - I'm bored with that, time for something new
If not having a 3 is what it take to ave a company still make great 1/2 then fine.
Would you want them to do a game they aren't excited about making?
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Less people playing? gosh, who would expect that in an ancient game.
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Enders Game
Re:Ansible (Score:4, Informative)
Rocannon's World by Ursula K. Le Guin [wikipedia.org]
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Oh- right... I remember now that in the book its named after some other SciFi, but I never knew the source.
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I am nerd. Hear me roar.
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First, for pedantic clarity, no "information" is transmitted through acts of fiddling with entangled bits. The "information" is transmitted as the entangled particles are moved to their respective endpoints (at no more than the speed of light), and though further actions may "change the outcome" (the exact meaning of which requires rather subtle interpretation, and can be framed within many not-incompatible understandings of QM), they cannot "transmit information".
Your question, then, is no different in the
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If you absolutely trust SSL v2 to be un-crackable, then there's no "point" to better communications. However, if there is the least bit of worry that classical cryptography can be broken (either due to flaws in the algorithm that a super-smart mathematician might discover, or "brute-force" solutions by quantum computers --- the jury is still out whether such is possible), then quantum transmission channels offer a new "layer" of security not vulnerable to clever mathematicians or super-powerful (quantum) co