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Scientists Teleport Information Between Ions a Meter Apart

Soulskill posted more than 5 years ago | from the perfecting-those-heisenberg-compensators dept.

Transportation 220

erickhill writes with word that scientists from the University of Maryland have successfully transferred information from one charged atom to another without having it cross the intervening space of about one meter. The academic paper is available in the journal Science, though it requires a subscription to see more than the abstract. Scientists have previously teleported unmolested qubits between photons of light, and between photons and clouds of atoms. But researchers have long sought to teleport qubits between distant atoms. Light's high speed of travel makes photons good transporters of information, but for storing quantum information, atoms are a much better choice because they're easier to hold on to. 'This is a big deal,' comments Myungshik Kim, a quantum physicist at Queen's University Belfast in the United Kingdom. 'To store information as it is in quantum form, you have to have a teleportation scheme available between two stationary qubits. Then you can store them and manipulate them later on.'"

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Scientists Teleport Information Between Ions (5, Funny)

Anonymous Coward | more than 5 years ago | (#26584005)

Are they positive?

Re:Scientists Teleport Information Between Ions (2, Insightful)

v1 (525388) | more than 5 years ago | (#26584381)

MPF. that's the most entertaining one-liner I've read in days...

Re:Scientists Teleport Information Between Ions (0, Redundant)

ExtremePhobia (1326407) | more than 5 years ago | (#26584719)

Are they positive?

ha, I see what you did there!

Re:Scientists Teleport Information Between Ions (-1)

Anonymous Coward | more than 5 years ago | (#26585055)

Are they positive?

They're H.I.V. positive.

Unmolested? (5, Funny)

PhrostyMcByte (589271) | more than 5 years ago | (#26584031)

Scientists have previously teleported unmolested qubits....

Qubit molester insists entanglement was consensual, stay tuned for details at 11.

Re:Unmolested? (5, Funny)

jd (1658) | more than 5 years ago | (#26584555)

In breaking news, the molester has been ordered to both sign and not sign the Atomic Sexual Deviancy Register at the same time.

Sounds neat, but I'm confused... (4, Interesting)

Chris Burke (6130) | more than 5 years ago | (#26584059)

All sources regarding quantum entanglement/teleportation are quite adamant that you can't use it to actually send information instantaneously. Despite there being "spooky action at a distance", any discernible information had to be transfered when you separated the photons themselves at sub-light speeds. In this case it would be atoms, but I assume it still applies? The article lists applications as super-fast quantum computers (I guess any functional quantum computer could be considered fast at what it does) and quantum encryption (a real application I've heard applied to quantum teleportation, though the encrypted data itself still has to travel at c or less).

So, am I right, and this is basically the same ol' non-instant-communication but still quite cool kinda teleportation, only using atoms instead of photons? I'm just checking.

Re:Sounds neat, but I'm confused... (2, Interesting)

Snowtred (1334453) | more than 5 years ago | (#26584097)

Yeah, I know a little about Quantum, but this kind of teleportation stuff still confuses me. I know there is some kind of logic argument that shows that no actual information can be relayed by this means, but how exactly is the information being transfered? Is it at lightspeed, or something weirder?

Re:Sounds neat, but I'm confused... (3, Interesting)

Normal_Deviate (807129) | more than 5 years ago | (#26584123)

As I understand, the essence of teleportation is that collapsing the wavefunction of the first particle (by measuring it) instantly collapses the wavefunction of the second particle. What I don't understand is why this does not represent transmission of the information that the first particle has been measured. Is it not possible to test whether the second particle's wavefunction has been collapsed by, say, sending it through slits?

Re:Sounds neat, but I'm confused... (4, Informative)

Anonymous Coward | more than 5 years ago | (#26584383)

If you send a single particle through a slit, you'll get a single spot. If you send many particles through slits, you'll get many spots, just as if you hadn't used entanglement -- they'll be all over the place. Either way, you won't know whether the wavefunction was collapsed by your observation or prior to it by the collapse of an entangled particle's waveform.

Say particles A and B are entangled, and you are in a position to observe B, but not A. You have no way to know whether A has already been observed, because B will look the same to you either way, unless you already know the state of A.

Re:Sounds neat, but I'm confused... (1)

Normal_Deviate (807129) | more than 5 years ago | (#26584455)

This confuses me further. Are you saying there is no way to determine whether particles are interfering with themselves, or others, due to quantum indeterminacy?

Re:Sounds neat, but I'm confused... (4, Informative)

mhall119 (1035984) | more than 5 years ago | (#26584653)

You can't determine if a particle is in a super-position or not, because any measurement of it will instantly collapse the waveform on both particles, and if you collapse yours first you will be unable to receive the information being transmitted by the other. You will need to know that the other entangled particle has already been collapsed, before you read yours, and that information still has to get to you by a conventional method.

Re:Sounds neat, but I'm confused... (1)

Normal_Deviate (807129) | more than 5 years ago | (#26584717)

I thought the essence of the 2-slit experiment was that you can detect quantum indeterminacy without measuring the quantum state, and hence without collapsing the waveform, by observing whether the various possible quantum states are interfering with each other. In the case of 2 slits, if you get fringes you have indeterminacy (particles are going through both slits) and if you get spots then the wavefunctions are collapsed (the particles have been forced to choose a slit). I assume there is an analogous test to see whether particles have been forced to choose their polarization. This seems to be all you need for instant transfer of the message "I have measured the polarization".

Re:Sounds neat, but I'm confused... (2, Interesting)

mhall119 (1035984) | more than 5 years ago | (#26584817)

The 2-slit experiment observed quantum super-position, not entanglement. The quantum state was measured when the photons hit the opposite wall, and that measurement only measured the collapsed state, not the super-position. The super-position was only observed in the pattern of interference in the collapsed states.

The super-position being measured was caused by the photon passing through the two-slits, so even if you took an entangled photon, collapsed it's partner, and sent it through the double-slit, it would still be in a super-position with regard to which slit it passed through, regardless of anything that happened to it's partner.

Mod patent up. (3, Informative)

Hurricane78 (562437) | more than 5 years ago | (#26584485)

Yeah. I will try to give a simplified explanation to non-experts (I'm just a curious guy myself):

First you entangle two particles. Then you let one travel somewhere. (If at bumps into another particle on that way, the particle loses the entanglement.)
Now if you "measure" the first particle, the "wavefunction" (the entanglement) of both particles collapses in a specific way.

By measuring that traveled particle, you can get the information on how the other particle got manipulated when it lost the entanglement.
The nice thing about this is, that it is instantly. There is no measurable delay.

So you could theoretically entangle a ton of material with another ton of material, and then send the first ton up to some remote planet. (Which of course would take very long. But you could send it at very high speeds which no human could survive too. For example by using a rocket that uses nuclear explosions as propulsion.)
Say you have defined, that you can use 0.5 kg of material every year for each side, and split the ton in such "blocks". Then you just write the outgoing 0.5 kg block (you collapse the entanglement) over the year, and read the incoming 0.5 kg block at the end of every year. By using a special encoding, you can detect where the data ends, and where the data collapsed trough your measurement. Or you just pipeline the to-be-written data on both sides, and read at the end of every month, week, day, hour, minute, second... whatever is most reasonable. (Making it a buffered transfer of blocks.)

This would give you a thousand years of infinite-speed (depending on your read rate) communication with the bandwidth of 0.5 kg of material per year (~1,37 g per day). (The amount of bits depends on the material.)

Re:Mod patent up. (4, Informative)

EdZ (755139) | more than 5 years ago | (#26584659)

Oh, if it were that easy. When you collapse the wave function my measuring one 'end' of your hypothetical particle-block, you: have NO WAY of influencing HOW it collapses, and thus cannot send any information to the other 'end'. You cannot determine what spin you will observe, only that the opposite spin will be observed on the other particle.

Re:Mod patent up. (1)

Arguendo (931986) | more than 5 years ago | (#26585241)

IANAP but am curious.

If you can still control WHEN it collapses, can't you send information as long as both sides have awesome time references? E.g., if it collapses on an even second, it's a 1, and if it collapses on an odd second, it's a 0. I understand that practical applications would be enormously complex, but it seems like you should be able to send information in principle if you can control some aspect of it.

Re:Mod patent up. (3, Informative)

Chandon Seldon (43083) | more than 5 years ago | (#26585409)

Unfortunately, you can't do either of the things you want to do. Relativity says you can't have synchronized clocks and quantum mechanics doesn't give you any way to know when/if the wave was collapsed.

Re:Mod patent up. (1)

plnix0 (807376) | more than 5 years ago | (#26585287)

There are different ways of measuring, each of which have a different effect on the particle. When measuring an electron, you can orient your measuring device at any of three different perpendicular angles. The angle at which you measure affects the probability of the entangled particle registering at the (opposites of) that angle and the other two angles. See here [ncsu.edu] .

Re:Mod patent up. (3, Insightful)

tylerni7 (944579) | more than 5 years ago | (#26584661)

I don't think that is how it works (although IANAP)

If you check to see if a block you have is collapsed, then suddenly it becomes collapsed, even if it wasn't before. That means you can't tell what it was supposed to look like before.

The other option is to only look at the entangled matter after you are sure it has collapsed, and see how the collapsing happened. However, this is also impossible. The way the qbits collapse is completely random, so you can't get any useful information out of reading them.

The best way to think about it is you have two coins taped to each other head to tail or something.
Then the coins are flipped, and separated without looking at them. Then take these coins to opposite ends of the universe.
Now, as soon as one coin is observed, the value of the other coin is known as well. However, looking at either coin does not help to relay information. The only way to do that would be to know how the coin was going to land before looking at it. Or to be able to somehow observe the coin and know if the other has been observed.

Re:Sounds neat, but I'm confused... (1)

bennomatic (691188) | more than 5 years ago | (#26584147)

IANAPhysicist, but my understanding is that while light speed is still an issue in physical space, the information sharing is truly instantaneous in this sort of quantum entanglement. It's not a short delay as light travels that distance, but instantaneous.

I think the way to think of it is this: there's another (or maybe many other) dimensions in the universe that our feeble minds can't perceive. They still exist, though, and things that may appear to be far apart in space (or even time-space) may be right next to each other in these other dimensions.

So when asking if there is a necessary delay due to the speed of light, you might be asking the wrong question, since it may seem like the light has to travel great distances across time-space from our perception, but across dimension N, it's right there.

My metaphor is flawed here, but when standing on UC Berkeley campus, it's a looooong way to the Transamerica Pyramid in SF if you go east, not so bad if you go WSW.

Re:Sounds neat, but I'm confused... (1)

Chris Burke (6130) | more than 5 years ago | (#26584191)

IANAPhysicist, but my understanding is that while light speed is still an issue in physical space, the information sharing is truly instantaneous in this sort of quantum entanglement. It's not a short delay as light travels that distance, but instantaneous.

Well the waveform collapse is instantaneous, yes, but as the WP [wikipedia.org] says, you can't actually use it to communicate information from one end to the other.

I really don't understand the physics of why you're not really sharing information when the waveform collapses. All I understand is that due to Relativity and time dilation, if you could communicate instantly, you could send messages backwards in time and violate causality.

Re:Sounds neat, but I'm confused... (1)

Hurricane78 (562437) | more than 5 years ago | (#26584537)

You would not violate causality. If you transmit the information about some bet from yesterday from A to B, and it reaches B yesterday, and B would instantly send it back, then it would reach A instantly after A transmitted the information.

But I also wrote above [slashdot.org] , how you could actually transmit information with it. I remember this from a "Spektrum der Wissenschaft" (German version of the "Scientific American") special issue.

Re:Sounds neat, but I'm confused... (2, Informative)

Jamu (852752) | more than 5 years ago | (#26585199)

Relativity implies that if information goes from A to B instantaneously for some observers, it also goes from A to B in finite time for some other observers. For all the other observers it goes from A to B in negative finite time, from B to A, in other words. For causality, for A to cause B, then information must always travel from A to B.

Any instantaneous wavefunction collapse cannot transmit information from distant locations, it must create new information for those locations, i.e. a random value.

Re:Sounds neat, but I'm confused... (1)

narcberry (1328009) | more than 5 years ago | (#26584157)

I just don't get it.

You "entangle" two atoms creating the qubit. You separate the atoms, then read the qubit?

Isn't the information already present in the entanglement, prior to the separation? Isn't it like spray-painting two objects red, sending them to opposite parts of the world and then proclaiming you've got a way to teleport information across the world, but can only send one message, "red" ?

I'm sure with all the hype I must just misunderstand the whole thing.

Re:Sounds neat, but I'm confused... (0)

Anonymous Coward | more than 5 years ago | (#26584209)

Nope. That is pretty much it. Except they anticipate being able to use one of the red rocks to turn the other one blue... and by "they", I mean the uninformed journalists and scientists looking for funding.

Re:Sounds neat, but I'm confused... (1)

Hurricane78 (562437) | more than 5 years ago | (#26584563)

Wrong. In Vienna they are transmitting entangled particles trough the air of half the city (between two towers) right now, and then when they reached the target, they can change the local entangled particle. Thereby instantly changing the remote particle.

So please stop trolling and inform yourself

Here's how it works, in simple words [slashdot.org] .

Re:Sounds neat, but I'm confused... (1, Interesting)

Anonymous Coward | more than 5 years ago | (#26585255)

no you are wrong, the posts above you are closer.

as you said in the post you linked, you are "just a curious guy". please don't deny most of the last century of physics just because something seems cool when you don't have any understanding of it.

thanks.

Re:Sounds neat, but I'm confused... (2, Insightful)

Chris Burke (6130) | more than 5 years ago | (#26584227)

Well, I think that's roughly the essence of why you can't send information instantly. All information about the qubits is actually sent with the qubit itself as you separate them to whatever arbitrary distance you're going to do your 'teleportation' trick. It's a little less obvious to me exactly why that is... my understanding is that it's kinda like you have both a black and red marble and you send one around the world, well when one guy checks and sees that his marble is red, the other guy instantly knows that his marble is black. But the first guy doesn't get to pick black or red, and you always knew that the one marble would be the opposite color of the other, so you don't really know anything you didn't before.

But I'm not really sure if what I'm saying there is even close to right.

Re:Sounds neat, but I'm confused... (4, Informative)

v1 (525388) | more than 5 years ago | (#26584431)

you have both a black and red marble and you send one around the world, well when one guy checks and sees that his marble is red, the other guy instantly knows that his marble is black.

More to the point, the other guy can find out his marble is black, but only if you communicate to him that your marble was red. Thus information was transferred, but you have to communicate by other means to make it meaningful, which defeats the purpose. It's like sending someone an encrypted message over an insecure channel. Great until you realize you now have to send him the key over the same channel. Sure it's encrypted, but the means of making it useful renders it ineffective.

Re:Sounds neat, but I'm confused... (2, Funny)

Chris Burke (6130) | more than 5 years ago | (#26584557)

It's like sending someone an encrypted message over an insecure channel. Great until you realize you now have to send him the key over the same channel. Sure it's encrypted, but the means of making it useful renders it ineffective.

Sure you can, you just need to use public key encryption. So I guess you're saying we need public key quantum entanglement?

Just kidding, thanks for the clarification. :)

Re:Sounds neat, but I'm confused... (2, Interesting)

drinkypoo (153816) | more than 5 years ago | (#26585321)

So I guess you're saying we need public key quantum entanglement?

Wouldn't it be hilarious if that turned out to be the case? If you just knew enough about the other member of your pair, that you could actually transmit information? It would make your comment one hell of a Doug Adams-type footnote.

Re:Sounds neat, but I'm confused... (2, Funny)

jd (1658) | more than 5 years ago | (#26584561)

Which goes to prove that teleporting physicists have lost their marbles.

Re:Sounds neat, but I'm confused... (1, Interesting)

Anonymous Coward | more than 5 years ago | (#26584319)

I just don't get it.

You "entangle" two atoms creating the qubit. You separate the atoms, then read the qubit?

Isn't the information already present in the entanglement, prior to the separation? Isn't it like spray-painting two objects red, sending them to opposite parts of the world and then proclaiming you've got a way to teleport information across the world, but can only send one message, "red" ?

I'm sure with all the hype I must just misunderstand the whole thing.

I am a physicist. This is absolutely correct. The whole language is convoluted and based on false premises... teleportation? Give me a break.

Re:Sounds neat, but I'm confused... (1)

MoellerPlesset2 (1419023) | more than 5 years ago | (#26584169)

In this case it would be atoms, but I assume it still applies?

Yes. Setting up the entangled state here requires both atoms to emit photons, so that occurs at light speed.
It follows the same old rules. Although the state of one atom, once measured, will affect the other atom instantaneously, there's no possibility for FTL communication.

Re:Sounds neat, but I'm confused... (1)

Chris Burke (6130) | more than 5 years ago | (#26584251)

Yes. Setting up the entangled state here requires both atoms to emit photons, so that occurs at light speed.
It follows the same old rules. Although the state of one atom, once measured, will affect the other atom instantaneously, there's no possibility for FTL communication.

Okay, can you clarify for me why exactly you can't? Is it because you can't actually control what state the measured atom, and thus the distant atom, will take?

Re:Sounds neat, but I'm confused... (1)

AaronLawrence (600990) | more than 5 years ago | (#26584389)

Yes, you definitely can NOT control the state. All you can do is measure the unknown state, find out what it is; and the other end will see the same state when it measures. Which of course tells you nothing of use (no information).

Re:Sounds neat, but I'm confused... (1)

plnix0 (807376) | more than 5 years ago | (#26584965)

Yes, you definitely can NOT control the state. All you can do is measure the unknown state, find out what it is; and the other end will see the same state when it measures. Which of course tells you nothing of use (no information).

Actually, the other end will see the opposite state. But it's the same information-wise.

Re:Sounds neat, but I'm confused... (5, Informative)

MoellerPlesset2 (1419023) | more than 5 years ago | (#26584465)

Okay, can you clarify for me why exactly you can't? Is it because you can't actually control what state the measured atom, and thus the distant atom, will take?

Sure, I'll try: A quantum 'entangled' state means that two systems are in an 'undefined' state in the quantum sense, that are interdependent.
When one is measured, the other one will _instantanously_ adopt whatever state is 'required' to complement the other one. So one 'knows' instantly what the other is doing, so to speak. Which means a sort of information has been transferred at FTL speed.

The reason why this can't actually be used for communication is twofold: One is exactly as you said: Because you can't know which state you'll measure, you can't transfer information through that alone. The second reason is that, an entanglement between two systems occurs only if there's an (unmeasured) interaction between them.

That means you either separate the two systems from each other (as in the classic example of entangled photons moving apart), or as in this case, by letting them interact with photons - that travel at light speed. Either way though, light speed is the best you can do.

Re:Sounds neat, but parent needs a MOD UP (1)

Chris Burke (6130) | more than 5 years ago | (#26584509)

Thank you for the explanation, that was very helpful.

One more question, about measurement. Is there any way to know that measurement has taken place at the other end and your local qubit has collapsed? Or would determining that constitute a measurement in and of itself, meaning if it hadn't been collapsed it then would be so you wouldn't know what happened? I mean, I know the answer is you can't communicate instantly, I'm just figuring out why (mostly to help explain to people with roughly my same layman's understanding of physics why instant communication is impossible).

Re:Sounds neat, but parent needs a MOD UP (1)

MoellerPlesset2 (1419023) | more than 5 years ago | (#26584953)

One more question, about measurement. Is there any way to know that measurement has taken place at the other end and your local qubit has collapsed? Or would determining that constitute a measurement in and of itself, meaning if it hadn't been collapsed it then would be so you wouldn't know what happened?

A good question. Now, determining if the thing has collapsed would require a measurement. Any interaction that could be used determine the state is a measurement of the state. But, that doesn't mean it's impossible to tell the difference, in the sense that we still know that's what happens.

Consider the opposite scenario: One system does not or can not 'know' that the other has been measured. That constitutes what they call a 'local hidden variable theory'. In other words, that the state of the system/particle isn't actually undefined and never was - it had a 'hidden' value, one that you just didn't know about until you measured it. That's the only alternate explanation for how the thing can 'know' which value to assume once it's measured (e.g. clockwise polarization for a photon if it was entangled with a photon that'd been measured as counterclockwise-polarized)

I'm almost hesitant to call it an 'alternative' explanation, because it's really the simpler idea. The states aren't genuinely undetermined, it's jus that we don't know what it is. However, it's also the wrong explanation - because of http://en.wikipedia.org/wiki/Bell's_theorem [wikipedia.org] . A brilliant bit of work that showed you could in fact test and measure whether there were such local hidden variables. There aren't. Quantum weirdness won the battle.

So you can tell that the states are genuinely undefined, and you can tell that this collapse occurs instantly. But you can't tell whether the collapse has actually occurred in any particular case. Now that I think of it, if you could, it would allow for FTL communication since you could communicate by, say, measuring or not measuring one of the particles at some predetermined points in time.

Re:Sounds neat, but parent needs a MOD UP (5, Informative)

getuid() (1305889) | more than 5 years ago | (#26585059)

Is there any way to know that measurement has taken place at the other end and your local qubit has collapsed?

Crash course in quantum mechanics, perhaps this explains it: a binary quantum mechanical system is in a linear superposition of states A and B. That is, it is either 100% A, or 100% B, or anything in between; for example 70% A and 30% B.

Now if you measure, you would only get "pure" results, i.e. purely A or purely B. If the system was pure (i.e. 100% B) before the measurement, you get what it was. If the system was mixed (say, 70-30), and you had the chance to measure the system more than once, then you get A in 70% of the cases, or B in 30%. For example: make 1000 copies of the system, and measure each of them. Roughly 700 (give/take a few) would be A, roughly 300 would be B.

The biggest problem is that you don't have 1000 exact copies -- unlike with classical information, basic QM forbids cloning of a system. So you basically have one shot, and if you happen to measure B, you'll never know whether it was because of a 100% pure B state, or simply because you "got lucky".

I mean, I know the answer is you can't communicate instantly, I'm just figuring out why (mostly to help explain to people with roughly my same layman's understanding of physics why instant communication is impossible).

While the "quantum information" is being transfered instantaneously, the problem is that the quantum state is not transfered 1:1 onto the target. It is ... "twisted". Imagine that like x*A+y*B (-> teleport ->) y*A+x*B. Now you know that the numbers x and y mean the same in both systems -- you just don't know exactly how they would be twisted after the teleportation. There are 4 possibilities how they can be twisted, and all 4 are equally probable, there's nothing you can do to favor the one over the other.

However, after the teleportation, the guy at the source can tell how they have been twisted (because the teleportation act itself is a measurement, which's result tells him exactly what happened), but the guy at the target does not.

So at first, even if the guy at the target knows that the atom has been "teleported", he stil doesn't know which one of the 4 twisted flavors of the original atom he got. If he just takes a "wild guess" and tries to measure, he'll get a statistical result which reveals absolutely no information about the actual coefficients.

The target-guy needs the source-guy to tell him which of the 4 twists occured, or in short: needs an information transfer in order to be able to "untwist" his atom and have an exact copy.

Again, the important part is that if the target-guy does not "untwist" his atom, but instead decides to go away and measure it anyway, he'll have an overall chance of 50-50 (regardless of the original x and y) to measure either A or B, so there's no information whatsoever that he could gain, not even from repeating the experiment.

It's the "twist" that makes the twist with teleportation... :-)

Re:Sounds neat, but parent needs a MOD UP (1)

Allicorn (175921) | more than 5 years ago | (#26585173)

Cracking explanation. Cheers!

Re:Sounds neat, but I'm confused... (2, Insightful)

v1 (525388) | more than 5 years ago | (#26584459)

Although the state of one atom, once measured, will affect the other atom instantaneously, there's no possibility for FTL communication.

The one part of that conclusion I don't get (and I've seen it several times to this point in the thread) is this: Why can't it relay binary information? If I entangle them, separate them, then either DO or DO NOT measure the first, and then measure the second, won't that tell me if the first one was measured or not?

Hmmm thinking on this I have to ask for clarification on the purpose of the measuring. I was assuming when you say you measure it, it's an on/off kind of thing. Is it more correct to say that in my above scenario, the way to tell if the second measurement produces information, is to compare it to the measurement of the first? That makes more sense as to why it's a pointless exercise. Because after taking the second measurement, the measurement itself is not enough, you have to compare it with the first measurement? Which requires communication which you are trying to avoid?

Re:Sounds neat, but I'm confused... (2, Informative)

blueg3 (192743) | more than 5 years ago | (#26584695)

No, it doesn't. View it from the perspective of the two measuring parties. We'll call them Abe and Bob.

Each particle has a 50% chance of being in one of two states, + or -. Entanglement means that if Abe's particle is +, Bob's is -, and vice versa.

Abe measures his particle. Regardless of if his particle is + or -, that doesn't tell him if Bob measured his particle or not. While the values of the measurements are dependent on one another, without information from the other measuring party, the measurer can't tell the difference between the entangled and collapsed states.

Re:Sounds neat, but I'm confused... (1)

plnix0 (807376) | more than 5 years ago | (#26585083)

The one part of that conclusion I don't get (and I've seen it several times to this point in the thread) is this: Why can't it relay binary information? If I entangle them, separate them, then either DO or DO NOT measure the first, and then measure the second, won't that tell me if the first one was measured or not?

The 'two' are really one system. If you measure the second, you will get the value of the second. From this, you will also know the value of the first, in essence measuring it at the same time. The values of both will be "collapsed". You won't know whether the first had already been measured, because whether it had been or not, all you get by measuring the second is its value. Not the meta-information 'has-been-measured-before'.

Re:Sounds neat, but I'm confused... (2, Informative)

plnix0 (807376) | more than 5 years ago | (#26584207)

Right. The abstract:

Quantum teleportation is the faithful transfer of quantum states between systems, relying on the prior establishment of entanglement and using only classical communication during the transmission. We report teleportation of quantum information between atomic quantum memories separated by about 1 meter. A quantum bit stored in a single trapped ytterbium ion (Yb+) is teleported to a second Yb+ atom with an average fidelity of 90% over a replete set of states. The teleportation protocol is based on the heralded entanglement of the atoms through interference and detection of photons emitted from each atom and guided through optical fibers. This scheme may be used for scalable quantum computation and quantum communication.

So yes, this is not true "teleportation". It relies on light actually moving from one atom to another through optical fibers.

Re:Sounds neat, but I'm confused... (3, Informative)

sarkeizen (106737) | more than 5 years ago | (#26584273)

"teleportation" always seems to lead people to the wrong conclusions. This is about transferring the informational content of a qubit. Which you can't perfectly represent with a classical system. I can see how this as the one commenting physicist claims is a "big deal" when it comes to building quantum computers. But it's not about instantaneous matter transport or superluminal communication.

I'm not sure what the article meant by ultra secure "quantum communication". Quantum teleportation *is* a quantum communication *channel* but it's unclear what kind of security they are talking about. Perhaps "Quantum Encryption" but that's another term that often sends people down the wrong track.

Re:Sounds neat, but I'm confused... (0)

Anonymous Coward | more than 5 years ago | (#26584481)

Quantum Physicists are the only people in the world who could take random crayon, break it in half, put each half in a box, send each box halfway around the world, open both boxes at the same time, and call the fact that the crayons are the same colour at that instant "an instantaneous transfer of information".

Anyone else looking at that exchange would say "fuck, we seriously fucked up these equations, even if they do model reality pretty closely." Quantum Physicists say "fuck, that's weird... but these equations do such interesting things, they must be how reality works on a fundamental level!"

Yeah, it's mostly just an issue of terminology, but if you say "information hasn't been exchanged at this point", but by that point the relation between states has been firmly established, then information has been pretty well fucking exchanged, even if you don't know how.

Re:Sounds neat, but I'm confused... (1)

shadowbearer (554144) | more than 5 years ago | (#26584549)

  You could send something as simple as a yes/no - yes, I've read your message , or no, I haven't.

  Add a few more entanglements to it, and you could send more. One time pad X wrt x. If this particular part gets read, yes; if that other part doesn't get read, no.

  On/off? requiring a shared sequence.

  Someone who understands it better, correct me and be more clear, please.

SB

Re:Sounds neat, but I'm confused... (0)

Anonymous Coward | more than 5 years ago | (#26585277)

yeah I was thinking if you have 2 billion quantum entangled atoms, a billion on each side of some divide, numbered 1 to a billion, you could unentangle the atoms in that list that correspond to 0 and transfer a gigabit of information?

Re:Sounds neat, but I'm confused... (5, Funny)

TapeCutter (624760) | more than 5 years ago | (#26585307)

"You could send something as simple as a yes/no - yes, I've read your message , or no, I haven't. [snip] Someone who understands it better, correct me and be more clear, please."

Analogy:
I have two basket balls, one has a cat inside - I don't know which one.
I send one basket ball to you.
I open my basket ball (observation).
I find it empty so I can deduce the cat is in yours (no information is transfered to you).
I cannot tell if you have opened yours and observed the cat as dead or alive.
You open yours and find a dead cat (observation).
Information is transfered in the normal manner when you call me up and ask why I sent you a dead cat in a basketball.

Re:Sounds neat, but I'm confused... (1)

disputationist (1324927) | more than 5 years ago | (#26584635)

Apparently the use of the term 'teleportation' is causing a lot of confusion. In QM, two particles that have identical states (quantum numbers) are considered indistinguishable; if they were switched, you wouldn't know. TFA describes a process that allows an entire state to be transferred instantaneously from one particle (or system) to another, and since in QM they are the same, the particle has been 'teleported'. There is nothing superluminal here, since before the state can be transferred you have to send some information across at kosher speeds.

Re:Sounds neat, but I'm confused... (1)

Have Brain Will Rent (1031664) | more than 5 years ago | (#26584781)

AFAIK whether or not the information is somehow invisibly stored with the entangled entities and so travels with them as they are separated at V = C is an open question.

Scotty! (0)

Anonymous Coward | more than 5 years ago | (#26584071)

Beam me up!

Re:Scotty! (0, Redundant)

bluefoxlucid (723572) | more than 5 years ago | (#26584115)

We come in peace! Shoot to kill, shoot to kill, shoot to kill! We come in peace! Shoot to kill! Scotty, beam me up!

Beam me up (0, Redundant)

Cyrus20 (1345311) | more than 5 years ago | (#26584085)

Beam me up Scotty!!!

A quantum physicist? (1)

MoellerPlesset2 (1419023) | more than 5 years ago | (#26584087)

Is there any other kind?

Re:A quantum physicist? (1)

philspear (1142299) | more than 5 years ago | (#26584225)

An indiscrete physicist.

Re:A quantum physicist? (4, Funny)

ozphx (1061292) | more than 5 years ago | (#26584323)

You mean a qubit molester?

Re:A quantum physicist? (1)

PachmanP (881352) | more than 5 years ago | (#26584247)

well there's those string theory guys, but they might not actually be physicists...

Re:A quantum physicist? (1)

thatgun (221980) | more than 5 years ago | (#26585069)

Well, I think you know the answer to that.

All Scotties aside... (1)

samriel (1456543) | more than 5 years ago | (#26584119)

We know now that we can indeed transmit information through space. Now, all we have to do is find a way to kick Heisenberg's ass and precisely measure each particle, and transcribe that as information. In all seriousness, we could indeed be frickin' teleporting to work in the next 100 years. Or shorter. Let's hope we invent time travel first, so we don't have to.

Re:All Scotties aside... (1)

BiggerIsBetter (682164) | more than 5 years ago | (#26585245)

In all seriousness, we could indeed be frickin' teleporting to work in the next 100 years. Or shorter. Let's hope we invent time travel first, so we don't have to.

What makes you think there's a difference? Walking across town would appear instantaneous if you went back the precise amount of time it takes you to walk there, except that you'd be that much older when you arrived.

How fast is it really? (1)

alvinrod (889928) | more than 5 years ago | (#26584139)

TFA (The Science News article) states 'instantly' and I can't actually read the academic paper (bugmenot doesn't seem to have a working login) but does anyone who's more familiar with this area know whether or not it's actually limited to the speed of light, or if we're actually seeing something that's capable of moving faster.

The article makes it sound as though it's instantaneous, but has this actually been measured to show that it's instantaneous or is the relatively short distance at which the "teleport" is performed only making it seem as though it were instantaneous? The implications of something like that are freaking sweet, but I don't really want to get my hopes up.

No, they have not discovered the ansible... (1)

plnix0 (807376) | more than 5 years ago | (#26584327)

Any use of the word "instantly" is, quite simply, hype. It's instantaneous like an "instant message" is instantaneous. Not that this isn't a cool discovery; it is. But it's not teleportation and it's not instant communication.

Re:No, they have not discovered the ansible... (2, Informative)

93 Escort Wagon (326346) | more than 5 years ago | (#26584469)

Any use of the word "instantly" is, quite simply, hype. It's instantaneous like an "instant message" is instantaneous. Not that this isn't a cool discovery; it is. But it's not teleportation and it's not instant communication.

No, "spooky action at a distance" is indeed instantaneous. It's a quantum phenomena - it's not based on the information being transmitted (which would indeed be limited to the speed of light).

Re:No, they have not discovered the ansible... (1)

plnix0 (807376) | more than 5 years ago | (#26584831)

Right, but the transfer of information is still not instantaneous. Just the transfer of the quantum state.

Re:How fast is it really? (1)

ITEric (1392795) | more than 5 years ago | (#26584447)

I don't know about you, but when were talking about light traveling 1m vs. "instantly", I'd be pretty impressed if they could actually measure a difference.

Re:How fast is it really? (2, Informative)

blueg3 (192743) | more than 5 years ago | (#26584493)

You most certainly can measure the propagation time of light over distances of one meter. It takes on the order of 10^-8 seconds for light to travel 1 m, and we have time measurement devices better than ns. (Actually, using clever techniques, you can do way better than meters.)

A question that maybe someone might answer... (1)

joocemann (1273720) | more than 5 years ago | (#26584199)

From the article they are saying that the entanglement has occurred, etc.... they also say that they know the entanglement occurs 1/100M times or so.

My question... If observation destroys the situation they describe, how to they know the entanglement happened at all?

Anyone know?

Re:A question that maybe someone might answer... (2, Informative)

disputationist (1324927) | more than 5 years ago | (#26584569)

They know it was entangled because they prepared the state way. For example, if you have a spin zero particle that splits up into two particles, and you measure one as spin up, the other must be necessarily spin down, no matter how far away it is, because of the conservation of angular momentum. Or you can think of a neutral particle splitting into positive and negative ones. So I guess it is ultimately the consequence of some conservation law.

IANAP Questions for someone who is. (1)

John.P.Jones (601028) | more than 5 years ago | (#26584281)

Okay I am not a physicist, but am interested in understanding a bit more about what is going on here.

Is the following description (model) a reaonably accurate portrayal of what is happening here?

We have two atoms (A1 & A2) that are in two different (non-entangled) quantum states (Q1 & Q2), at two locations (L1 & L2) separated by 1 m, at which point we allow A1 to interact (quantum mechanically) with a photon which then is 'transmitted' along the vector (L2-L1) and is then 'received' at L2 and allowed to interact with A2 to evolve its quantum state. The process is repeated a finite number of times, after which A2 is left in a quantum state Q1 (the initial state of A1). Or does A2's state simply approach Q1 with some non-zero but bounded error?

If so, can you answer these questions and if not, how does the difference between my model of what is happening and what is actually happening effect the validity of the question and its answer (to the extent that it is still valid)...

Throughout these interactions is the state evolution of A1 minimal so that the state is still near or identical to Q1 and these two atoms are now entangled or is the initial atom A1 left in a vastly different quantum state Q3? Or perhaps we can exchange the two quantum states (obviously this would require bi-directional photon communication).

If the final state of A1 is different then its initial state, can we modify the procedure to allow A1 & A2 to converge on a common state Q3?

Is the 4-momentum part of this quantum state (obviously the position is not)?

If you are cloning a state Q1 which has a corresponding energy E1 how does that energy relate to the cumulative energy of the transmitted photons (I assume the process isn't reasonably efficient), and is that difference dependent on the initial energy of the A2 atom?

Just read it yourself (0)

Anonymous Coward | more than 5 years ago | (#26584407)

http://rapidshare.com/files/188497112/quantum_teleportation_486.tar.html

Consider this as a long and very detailed "quote" ;)

Please subscribe to Science magazine if you can.

Freedom of knowledge, teh internetz has you.

Re:Just read it yourself (0)

Anonymous Coward | more than 5 years ago | (#26584657)

Much appreciated.

Bell's theorem (1)

plnix0 (807376) | more than 5 years ago | (#26584283)

According to Bell's Theorem [wikipedia.org] , separated particles can be correlated such that observing one will affect the state of the other, disproving locality. However, the no-communication theorem [wikipedia.org] states that this cannot actually be used to communicate.

The idea of instant communication is quite fascinating, but it doesn't really apply to this study. The communication they showed is not truly instantaneous, as it relies on the transport of photons from one atom to another (read the abstract, which says as much).

Re:Bell's theorem (2, Insightful)

blueg3 (192743) | more than 5 years ago | (#26584503)

The teleportation is instantaneous. (A philosophy-inclined physicist might object to you applying the label "instantaneous", since it implies a signal is propagating instantaneously -- but there's no signal at all.) However, the teleportation cannot be used for communication without information transfer -- which means the communication is bound by the speed you can transfer that information (which is lightspeed).

Re:Bell's theorem (1)

MoellerPlesset2 (1419023) | more than 5 years ago | (#26585249)

You're talking about entanglement, not 'teleportation'. This uses entanglement but it is _not_ instantaneous in any way. It requires having each atom emit a photon, allowing for those photons to become entangled, then performing a measurement on them, and "classically" communicating the results of that measurement so that the 'receiving' end knows what phase to put on a microwave pulse that has the end result of recreating the state that's being transferred.

Bell's Theorem can do FTL comms just fine (0)

Anonymous Coward | more than 5 years ago | (#26584707)

Just arrange entangled pairs A+B of qubits in a line, separate the A's from the B's while preserving the linear order, and send the line of B's somewhere remote at less than lightspeed while leaving the line of A's behind.

Then encode some information as lengths of time pulses, and apply those lengths to the line of A qubits as intervals between adjacent qubit collapse (read each one to make it collapse). The corresponding B's will collapse instantly in the same order and with the same time intervals, and the information you encoded as collapse intervals is available identically and instantly at location B, regardless of distance. Note that the value to which each qubit collapses is irrelevant: data is carried by the time intervals between loss of entanglement in adjacent qubits in the line.

Since the encoded data was not carried by the slow-moving B qubits on their outbound trip, but is entirely new data available only at the time that the A's are collapsed, this is FTL transfer of information which can be used to communicate at arbitrary distance. Note also that two A+B pairs give you bidirectional communication, and this works instantly despite the time slip between A and B inertial frames on B's outbound journey. Time travel of information (forward in time in one direction and backwards in time in the other) is going to provide endless hours of heated debate. ;-)

Pity that you can use the entangled qubits only once. I guess outbound motherships are going to be carrying as large a store of them as they possibly can, and they're going to be priceless. (Particularly since qubits collapse rather easily so you need redundancy and a very robust encoding scheme to avoid data loss.)

And leave poor Einstein alone. He never did feel at home with QM, but liking it is not a prerequisite for being able to use it. Reality likes to be bizarre occasionally. ;-)

Re:Bell's Theorem can do FTL comms just fine (1)

plnix0 (807376) | more than 5 years ago | (#26584789)

Seems clever, but how do you detect disentanglement?

Bah! (5, Funny)

GaryOlson (737642) | more than 5 years ago | (#26584295)

My mother always knew what I had done without anyone telling her. Or whatever I was going to do before I took action. I hear other mothers have the same ability. Therefore, all mothers must exist in some state of constant quantum communication with each other.

Re:Bah! (1)

ustolemyname (1301665) | more than 5 years ago | (#26585305)

Mild correction: all mothers must exist in some state of constant quantum communication with their children.

A New Form of Wireless (2)

Nom du Keyboard (633989) | more than 5 years ago | (#26584433)

Adds a whole new meaning to the term: wireless.

Re:A New Form of Wireless (0)

Anonymous Coward | more than 5 years ago | (#26584619)

No, actually, it still means pretty much the same thing it always did. No wires.

Re:A New Form of Wireless (1)

markdavis (642305) | more than 5 years ago | (#26584669)

Absolutely. Quantum computing aside, the idea of wireless communications via entanglement is absolutely fascinating. It could lead to instant communication with anyone, just about anywhere in the universe! No towers, no RFI, and absolutely secure from point to point. The major downside is that you probably have to have a centralized "entanglement switchboards" to actually relay the communications from one person to another, since you can't entangle every device to every other possible device. So that would be the weak point for security and reliability (and big brother spying).

Anyway, I can imagine a day when my portable computer/communications device, whatever form that takes, can talk to just about anything, without ever having to think about where I am, and possibly with unimaginable runtime and unimaginable bandwidth.

Oh well, back to the wonderful world of cell towers and WiFi....

Don't know if I'd be concerned about the security. (0)

Anonymous Coward | more than 5 years ago | (#26585057)

For protection of information, there's still the encryption method of your choice.

And as far as prosecution goes, all the switchboard would tell you is the terminal - not the user, not the location, and if the terminal is modular (as many NICs and cell radios are), possibly not even the computer itself.

And it begins.... (1)

Proudrooster (580120) | more than 5 years ago | (#26584467)

Just think, if they can figure out how this works or at least how to exploit it. You could use these for secure long distance communication. No more cell towers, just entangle some particles, put one in a rack and the other in the cell phone.

I am curious to know if this "spooky action at a distance" as Einstein referred to it, is faster than light communication. We won't know this until we put one in a Mars rover and launch it. I would also be interested to know if these particles are entangled in another dimension outside of space time. I hope this can be figured out in our lifetime.

Re:And it begins.... (1)

blueg3 (192743) | more than 5 years ago | (#26584531)

It is not faster-than-light communication. We will know immediately, and do. (You don't need large time scales to test "immediate" communications -- we can measure that to sufficient resolution on Earth.)

I'm not sure your statement on "if [they] are entangled in another dimension" is really meaningful. Entanglement is a property of objects in quantum states.

You can already exploit it, though -- it's fairly similar to the basis for quantum "encryption" (by one definition), which is not encryption at all, but a form of communication that is impossible to intercept without rapid detection. You can create these states with photons, which is what is done. It's unreasonably complex to use outside of special applications and cool demos, though.

Damn... (4, Funny)

fenix849 (1009013) | more than 5 years ago | (#26584625)

Ok, who voted for the beammeupscotty tag?

I can't think of a worse place to be beamed, than 'up scotty'.

O, how about this for an explanation? (1)

ivoras (455934) | more than 5 years ago | (#26584703)

You have two entangled particles A and B and send particle B somewhere else. Then you take a reading of A and call this reading X. You don't really know what is the meaning of X - did you observe it first or did someone else observed B first but you do know that if someone observed B next he will certainly get reading X back to him. Thus it's useless for communication.

The only way this seems useful to me is if we need to keep something perfectly identical to something else, but it can't work that way either, since quantum effects don't work on bigger scales (nothing's preventing you from smashing particle B but it won't affect particle A at all, right?)

It's sort of pointless on a bigger scale - tear a piece of paper in the dark, then send one piece in another room, come back to the first one and turn on the light - you can certainly declare the the shape of the tear of the other piece will perfectly match what you have here :) In other words, there's no analogy we can use, at all, for any communication purpose.

what, no glitter involved? (1)

Eil (82413) | more than 5 years ago | (#26584741)

Hey physics types: So I take it this can in no way lead to the future development of the transporter [wikipedia.org] ?

Transmutation of elements. (0)

Anonymous Coward | more than 5 years ago | (#26584763)

This may be an enormous breakthrough but these scientists are wasting their time. They should be spending their time (and budgets) working on transmutation of elements. Then, we can turn gold into a much more desired substance, lead.

Apparently all our physicists have finally left /. (1)

dhudson0001 (726951) | more than 5 years ago | (#26584857)

...for kurzweilAI.net

Beam me up Scotty! (1)

AssTard (684911) | more than 5 years ago | (#26585143)

Theres no intelligence life down here! LOL!

Just for clarification... (1)

arclyte (961404) | more than 5 years ago | (#26585153)

This experiment is about the teleportation of qubits, not to be confused with the 1982 experiment involving the teleportation of Q*bert, wherein, after falling off the bottom of his pyramidal cubes, the protaganist would teleport back to the top of said pyramid.

God's Rootkit (0)

Anonymous Coward | more than 5 years ago | (#26585181)

With this modern parade of hard-to-grasp physics discoveries, it feels as if we may soon get admin access to the universe. I can't wait, as that means we will soon be able to flood Heaven with spam.

G0d, Mak3 her sore w ur MonSteR MemBER!!!

My understanding... (1)

MisterMikeyG (1454529) | more than 5 years ago | (#26585273)

This type of thing is interesting in the realm of secure communications. Information does and can not travel faster than the speed of light, so don't get hung up on that. What you DO have is a communication medium like, say, fiber optics. By using a quantum medium, the state becomes disrupted upon measuring it. This means that each end can account for the other's measurement and thus be unconditionally certain that no other party has read the transmitted message. This is ideal for operations such as key distribution. I'd note that this process would actually be slightly slower to communicate than fiber optics. You have to send a traditional message over a non quantum wire communicating to the other party when and how to measure the quantum state. It's only application, arguably, is in network security. Quantum COMPUTATION, however, is a different subject. This is not that.

Leapping (0)

Anonymous Coward | more than 5 years ago | (#26585371)

So this has nothing to do with the Quantum Leap guy?

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