Macroscopic Quantum Entanglement

meckardt writes: "We laugh at the science fiction of such programs as Star Trek, but it can almost be stated as a truism that what is fiction today may be science tomorrow and engineering next week. Researchers at the University of Aarhus in Denmark report in the science journal Nature that they have been able to cause particles to interact over a distance using lasers. The effect, called quantum entanglement, has been observed before, but never with such large amounts of matter. Don't expect transporters next week, but it is interesting that this report hits the streets the same day that Enterprise debuts."

Comments

Wow

[man_ls]

I wonder how long it will take before we won't even need to go to McDonalds to pick up our food from the drive-through. We'll just teleport our cash there and get our food back, right into our microwaves, or some other instrument.

Yummy.

Re:Wow

[MadCow42]

Actually, you can't yet pick up "real" food at McDonalds... let them get past that hurdle first.

MadCow.

Re:Wow

[Courier]

'How about when energy and other resources becomes free? You are going to see more then the cost of gas if you teleport your food.

Nice.

[exceed]

Now school kids that have forgotten their lunch at home can have it beamed over to the local elementary school.

Re:Nice.

[Anonymous Coward]

Now school kids that have forgotten their lunch at home can have it beamed over to the local elementary school.

And bullies can beam it straight out of their pockets without their knowledge. :)

Good

[NitsujTPU]

Now... if we can throw an atom smasher on mars we can get decent bandwidth to our next rover .

Clarification...?

[melquiades]

As I've understood these experiments in the past, entanglement involes splitting a particle, or taking two existing particles, and "entangling" their states -- so that, for example, if you change the spin of one electron, its partner electron's spin also changes, even at a great distance (or something to this effect).

The application to faster-than-light information transmission is obvious. But teleportation? The article doesn't give enough specifics. Can anybody shed light on this? How would this experiment lead to a teleporter??

Re:Clarification...?

[Maditude]

An equally non-informative article is here: http://dailynews.yahoo.com/h/nm/20010926/sc/scienc e_quantum_dc_1.html
/me hopes they perfect teleporting that delicious Danish beer real soon now! :-)

Re:Clarification...?

[de Selby]

I've read that while the entanglement works without delay, information isn't transmitted at more than the speed of light.

But I have now idea why.

Re:Clarification...?

[mrseth]

I think their goal may be practical to quantum computing. I could explain this here, but I already did it here. Basically, you need to be able to create a quantum copier to create a quantum computer. Building a quantum copier is difficult because, due to the no-cloning theorem, arbitrary quantum states cannot be copied perfectly every time. You can either clone a subset of quantum states perfectly or you can copy arbitrary states with a certain probability of failure.

Re:Clarification...?

[lkcl]

regarding teleportation. it's simple. when you fire one photon at another, they interact [they're waves, but also particles]. in this way, you get one photon passing through another, or you get one photon imparting "mass" to another photon, and a change of direction of the two photons, conserving momentum. when you fire one photon at an "entangled" pair, if the momentums are matched, then the "fired" photon can actually disappear at the location where it hits one of the "entangled" pair, and reappear at the location of the SECOND "entangled" pair. in this way, you have instant teleportation - of photons. now make that many photons, and you have instantaneous quantum communication it's not really FTL because it's actually the same photon that happens to have more than one point-of-presence in the physical universe. now, step that up to particles, instead of just photons, and you have instantaneous teleportation. however, i theorise that this would require some _seriously_ cohesive photons, which probably implies that they must have intelligence built-in to the photons, and it's at the word "intelligence" as associated with "photons" that i diverge from current "accepted" theories regarding the nature of the universe and i'm going to shut up because there is a lot more to learn than meets the eye.

Re:Clarification...?

[a_hofmann]

You are right, this quantum teleportation allows the transfer of particle states over distance. This is not about transporting matter. This will not allow us to build teleporters.

Further information and links at the research group from Austria that ran the first experimental verification of quantum teleportation.

Re:Clarification...?

[mocm]

You don't change their spin, you measure it and find that it is the same. Usually you measure a quantity that has a fifty fifty chance to give one or the other result. The interesting thing is that it always comes out the same for the entangled particles. No matter how far their separation in time and space.

You can't convey any information that way since you don't know what the result of the measurement will be. But somehow the particles "know".

For more information see their paper at http://xxx.lanl.gov/abs/quant-ph/0106057
and references therein

Re:Clarification...?

[|_uke]

The information does not travel through time/space. There is a direct link between the entangled particles so there is no travel involved. (Think of an indirect link as anything that requires travel, which means things like radio/light/etc anything used in todays form of communication.) Because of this, you are not traveling faster than light.

Of course the exact details of how this works I could not tell you.

The thing I love about this however, is not the practical uses here on earth. But accross space. We could have live internet connections between mars and earth, for example.

Another cool thing, instead of using any of the standard methods of connecting to an isp, you buy a 'node' from an isp you wish to use. From then on, reguardless of your location, you can use that node to connect through the isp's network. This means you could have a nice chat while sitting in your home on mars.

Interesting though... I wonder how differences in time/space between entangled particles would effect things...

If you travel near the speed of light, while communicating with someone through an entangled pair to someone who is on earth... What happens?

Will the modifications made to the entangled particle be reletive to the first particle?

hrm... suppose so... wow that would be weird.. LOL

Want to improve your download speeds? Fly faster :P

Re:Clarification...?

[renard]

Can anybody shed light on this? How would this experiment lead to a teleporter??

Well, this will get us into some of the most dangerous neighborhoods of quantum mechanics, but I'll see what I can do.

The quantum entanglement of two particles means that (just as you say) the behavior of one particle becomes perfectly correlated with the behavior of another. In the classic example case, two photons are generated with opposite polarizations. If you can transmit them a distance apart without any interference, then the photons will remain entangled, and a measurement of the polarization of one photon will have immediate implications for the polarization of the other.

Although this is very useful for quantum cryptography, please note that it will NOT allow you to transmit information any faster than the speed of light. To take the cryptographic example, it allows you to generate a safe one-time pad, known to both sides and to no one else, but you still have to transmit your actual message separately.

How can quantum entanglement be used for something like teleportation? Well, let us agree first that if I can produce a perfect quantum replica of a distant system, that is equivalent to teleporting the system. Any given electron (for example) is indistinguishable (in a very deep sense) from every other electron in the universe. So for teleportation all we need to do is reproduce a quantum state. You might say it's more akin to a quantum xerox machine than to most people's classical idea of teleportation.

Okay, so here's how it works: take your two quantum-entangled photons, and instead of simply measuring the polarization of the one nearby, get it to interact with a "target photon" that you want to teleport. If you set things up properly, and observe the outcome very carefully, then the interaction of the two photons on your end will cause the entangled photon - an arbitrary distance away - to enter a new state which is perfectly correlated with the state that your target photon had. Then, once you tell your distant collaborator about the exact outcome of the photon interaction on your side, your collaborator will be able to apply that knowledge to her entangled photon, and produce an exact quantum replica of your original target photon. Voila! Teleportation.

Note again that no faster-than-light communication is enabled by this. You still have to communicate a regular light-speed message between collaborators to get this to work. The actual experiment was carried out several years ago and is old hat by now. The current experiment improves upon previous efforts by entangling so many more (trillions!) particles.

The quantum entanglement of so many particles makes the actual teleportation of a similar number feasible, but one final note - even trillions of particles is many orders of magnitude less than the 10^27 or so particles in your average Starship Captain.

-Renard

Re:Clarification...?

[dragons_flight]

Here is a relatively straight forward discussion of the theory behind teleportation via quantum entanglement.

Whether information transfer is actually instaneous is a hotly debated topic in the relevant circles. General relativity forbids anything (including information) from going faster than the speed of light. The standard formulation of quantum mechanics absolutely requires non-localized information (ie knowing about two spatial seperated points simultaneously). This is just symptomatic of the fact that neither is a complete theory yet, and we still have interesting things left to learn about how the universe truly works.

Re:Clarification...?

[Coolumbus]

Pretty good explanation here:

http://www.qubit.org/intros/comm/comm.html

(Centre for quantum computation)

Re:Clarification...?

[jms]

I've always thought that an interesting science fiction scenario would be a future where teleportation is a day-to-day part of life, but instead of actually teleporting people to the new location, the equipment creates a new copy of the person at the new location, then destroys the old copy of the person at the original location, a minor detail of the teleportation process that is, of course, a well kept secret.

In this scenario, people happily teleport to work, vacation, the grocery store every day, never realizing that every time they step into a teleporter, "their" life comes to an agonizing end ...

until one person finds out ...

Any good examples of this scenario in "classic" sci-fi? I can't imagine I'm the first to think of it, but I've never actually run into it in my reading, and I haven't run into it in recent sci-fi either.

Re:Clarification...?

[Mythias]

This exact same scenario took place in an Outer Limits episode that I saw. The process involved making a copy and transporting that copy to another place, then destroying the original. But, as is standard Outer Limits fare, something went wrong and the transfer was unsuccessful. Therefore, the original was not destroyed. The next day they found out that the transfer WAS successful, but was reported incorrectly. So they had to destroy the orignal AFTER she'd already woken up and was told what happened. I'm not explaining it very well, but it was a good episode.

Re:Clarification...?

[Anonymous Coward]

Of course these scenarios are always predicated on the ability of humans to keep these kind of secrets. In reality, the organizational ability of humans is too weak to keep a secret of such importance.

Re:Clarification...?

[Anonymous Coward]

You ripped this off from the Outer Limits. Shame on you!

Their death would be less noticeable than going to sleep, and being exact quantum copies mean they are effectively the exact same person.
They wouldn't need to keep it a secret from me, unless they didn't destroy the original near-instantly.

Re:Clarification...?

[Anonymous Coward]

I'm afraid I'm missing something still. If you could (at least theoretically) "teleport" a couple trillion particles at faster-than-light, then surely the states of those particles themselves might be encoding information, which you then would have transmitted at faster than light. Or is it the *state* of the particle itself that you actually have to transmit at lower than light speed? In which case it would just be a sort of remote "3d printer" or "3d xerox machine".

Either way, I would settle for slower-than-light teleportation if it existed :) I can live without being teleported to the other side of the galaxy, but I would love to be able to eliminate the tedium of driving to work/gym etc every day.

Re:Clarification...?

[Anonymous Coward]

0:Redundant?

Who got up the moderator's ass today?

Re:Clarification...?

[de Selby]

I never meant to imply any travel was involved--just that many people have stated (and now on slashdot) that while properties and changes can be shared by two seperated particles instantaniously, any _information_ passed by such means could not "reach" the destination before a signal moving at the speed of light would.

Also, I don't understand how such a thing makes any sense. It seems contradictory to me.

Re:Clarification...?

[Anonymous Coward]

Actually a few Star Trek books mention this specifically, "Spock's World" by Diane Duane is one I think. The original is deliberately destroyed as part of the copying process; this is why you have people like McCoy always a bit on the nervous side.

A couple of episodes of TNG examined the transporter in a fair amount of detail; the episodes themselves were fairly naff, but the concepts introduced were interesting. For instance, the transporters on 1701-D contained copy buffers, so that in the event of an unsuccessful transportation the original (destroyed during the unsuccessful attempt) could be recreated at the source. A fairly sensible safeguard that might even have made McCoy happy :)

Re:Clarification...?

[Anonymous Coward]

Oh! One further thing, a very old book (in fact I believe it was the first authorised Trek novelisation, way back in the 70s) called "Spock must die!" (tacky title :) by James Blish also dealt with transporter effects. Specifically, the Enterprise encountered a shield which happened to be an exact mirror for transporters, so they ended up with a duplicate on board after a transporter attempt to the shielded destination - and the crew had to determine which of the two "originals" needed to be destroyed, after the event :)

Re:Clarification...?

[rabtech]

This has been dealt with in a variety of sci-fi literature, such as the Ender's Game series.

Time for the travellers on the ship passed much faster. So the communication device took the entire message and spaced it way out so that it appeared to the stationary receivers to be perfectly in-sync.

Similarly, to receive a message from a planet, the computers there took the message and "squished" it up so the information was transmitted much faster, and appeared to the receivers as "normal".

This is a gross oversimplification, but I think you get the picture.

Re:Clarification...?

[denshi]

The webcomic "Shlock Mercenary" (www.schlockmercenary.com) briefly explored this a few months ago. They took it one further, though. In the Schlock universe, interstellar travel is handled in a similar fashion, but it is controlled by one ancient race who allows no one else to see the inner workings of its operation. The reason for that is that rather than automatically destroying the original, the wormgate race interrogates the clone, extracting all conceivably useful info, and then destroys the original. The motive, and effect of this policy is that they gain detailed inside knowledge of the plans and discoveries of all the races who use their transport, which is to say all the powerful races; the wormgate aliens use this to prop up their rather shadowy empire. That's the main backstory, at least; "Schlock" proceeds like a conventional webcomic, returning only occasionally to the core of the plot advancement, namely the cast has invented a new warp drive that does not rely on the wormgate platform, and has growing evidence of the copying and interrogation.

I haven't seen any of this in classic sci-fi, so jms's question still stands.

Re:Clarification...?

[shaunak]

The application to faster-than-light information transmission is obvious.

Actually, faster than light information transfer using quantum entanglement is not possible. Suppose A and B have two entangled particles (one each), both kept isolated so that no measurements may be performed by mistake. A goes to Alpha Centauri, and B stays here. Now, assume the particles are electrons (to make it easy). If B wants to send a message (a single bit) to A, the obvious thing to do would be to perform a measurement on his electron so that its superposition of states breaks down to one single state, and A's particle takes the same state at the same time (yes, spooky action at a distance is what its called, and its faster than light). However, there is a catch. When B performs a measurements, if there are 4 states involved in the superposition, he can get any one of the four. It involves probability. So if he has already decided a code with A which says that if the particle's superposition collapses to state 1, it means this, and so on, he cannot be sure which state it will collapse into, and hence it is USELESS for transmitting information. I believe this is a result of the Bell Inequality. Faster than light information transmission is still impossible.

Re:Clarification...?

[Anonymous Coward]

But what, if the message is not the collapse in a certain state, but simply: If the state _changes_ (into whatever) it means : yes.

Re:Clarification...?

[Anonymous Coward]

That was me, sorry. He usually likes it, though.

Re:Clarification...?

[shaunak]

But what, if the message is not the collapse in a certain state, but simply: If the state _changes_ (into whatever) it means : yes.

But to verify change, you should know what state it was before. Once you've performed the measurement, the superposition collapses, and if B does this, A finds his particle in Bs state.
Trust me, faster than light information transfer is not possible.

Re:Clarification...?

[mcplusplus]

Is this like the Bell experiments, where two subatomic particles, separated by a great length of battleship-grade steel continued to spin in complimentary directions?

Re:Clarification...?

[esonik]

Quantum entagnglement cannot be used to transmit information, because you cannot tell into which quantum state the "sending" particle collapses.

The classical analogon would be two "entangled" dice - say both dice always show an identical number. However, being dice you cannot predict which number they show (or force them to show a certain number) and thus you cannot send any information (only random numbers).

The connection between quantum entanglement and the dice is that collapsing a quantum particle into an eigenstate (e.g. forcing an electron into a spin-up/down state) is like throwing a die: you never know into which eigenstate it collapses (i.e. you cannot predict whether the electron goes into spin up or spin down state).

Not true teleportation

[Wind_Walker]

This is actually NOT teleportation; this is akin to an episode of The Outer Limits I saw once where they create an exact copy of a person on the other end of a "teleportation" machine, and then destroy the copy that currently resides on the transmitting end. It's a great show, but I digress...

I'm amazed that this worked with "trillions" of atoms; this kind of phenomenon is usually restricted to very small, very energetic particles. But it's NOT teleporation. Teleportation involves taking an object from point A and moving it to point Z without crossing the in-between space, C through Y. This is like taking an object from point A, running it through the world's biggest and best Fax machine, then putting the result at point Z, without crossing C through Y.

Still, it's an interesting and ground-breaking result, one that (I hope) will make it past the peer review process, which kills more scientific papers than anything else.

Re:Not true teleportation

[Anonymous Coward]

I see, if only the people with PHD's watched outer limits, they could of svaed all that college money...

using quantum entanglement you could, in theory, make your particals have a hogher probabilty of existing at point b then at point a, hence the teleportation.

John Doliur, PHD.

Re:Not true teleportation

[sacrilicious]

But it's NOT teleporation. Teleportation involves taking an object from point A and moving it to point Z without crossing the in-between space, C through Y.

Those of you out there who are lazy and want a free lunch, don't forget that you have to cross through point B! And from what I hear, qualifications to cross through point B are especially rigorous; physicists trying to unravel teleportation have dubbed its essential conundrum as "the Point B obstacle".

Re:Not true teleportation

[dragons_flight]

Nature is a peer reviewed journal, and one of the more prestigious ones to boot. This means that there is nothing wrong (unless very subtle) with the setup or analysis of their experiment provided the data they report is accurate. Of course something might still be wrong with their results, but that will found out when other scientists try to replicate the experiement.

Re:Not true teleportation

[Anonymous Coward]

It's spelled particles,
but around here article
is spelled artical

:-(

Re:Not true teleportation

[ENOENT]

Nature is a peer reviewed journal, and one of the more prestigious ones to boot.

Damn, here I've been going under the misapprehension that nature is a big open place full of green things and other things that can poop on you.

Re:Not true teleportation

[Theodore Logan]

it's NOT teleporation. Teleportation involves taking an object from point A and moving it to point Z without crossing the in-between space, C through Y.

This is incorrect. Classical teleportation is defined as a scenario where the sender is given the classical description of an arbitrary quantum state while the receiver simulates any measurement on it. This is exactly what you argues it isn't. Besides, if the destinction you make is one worth making or not is an open philosophical question, i.e. one that is not resolved.

It's what I've always said: we should have a new moderation cathegory - "Incorrect".

Re:Not true teleportation

[stantron77]

My only question is where did B go?

Re:Not true teleportation

[Anemophilous Coward]

This is actually NOT teleportation; this is akin to an episode of The Outer Limits I saw once where they create an exact copy of a person on the other end of a "teleportation" machine, and then destroy the copy that currently resides on the transmitting end. It's a great show, but I digress...

This was also a concept in Micheal Critons(sp?) last book, "TimeLine". Quantum intanglement was perfected to allow individuals to cross over into other probabilities (ie: alternate universe theory). This could only be accomplished by destroying the existing object (person) in one universe and having it reassembled in another one. Slight impefections could creep in (random probabilities far greater from the norm of the universe they left) after many trips...much like over-faxing.

You're right in that it isn't true teleportation, but rather generating the right probabilities for an instance of matter to appear in another location. Sure it needs to be carried along a modulation-like system, but if you could increase the number of particles involved it will be quite impressive.

On those lines, many seem to think that Star Trek like teleportation just 'zoom', goes across space unhindered. But if you watch the shows, it would seem that the mechanism is similar, it sends the information through a modulated beam. Within the ship, the structure must have the ability to transfer this beam, hence they can beam around the ship (also note the frequency of the beam appears to be beyond visible range). As for beaming down to a planet, same thing. You notice they cant beam while their shields are up, because the carrier wave cannot pass the information through.

What the Star Trek teleporters have done is eliminate or reduce the amount of errors and changes in probablities that will arise after many, many, many teleports. The matter is effectively different after teleportation (random probability changes, but enough stay the same so that it still looks the same and exists in the same universe). I wonder what random changes they allow to matter in their teleporters; maybe you get hair that doesn't grow as fast anymore, or some other non-life threatening change.

- A non-productive mind is with absolutely zero balance.

- AC

Re:Not true teleportation

[Mandelbrute]

This is actually NOT teleportation; ... ... create an exact copy of a person on the other end of a "teleportation" machine, and then destroy the copy that currently resides on the transmitting end.

True - this is science and not magic. It will be the "murdering twinmaker" that you can read about in the SF written by those that think about their plot devices. In one novel it was justified by using the energy released in disintegration to provide most of the energy needed for reconstuction, and that there wasn't enough energy available to copy all of the matter that was being shipped about ohterwise.

Re:Not true teleportation

[chron]

First of all this article is talking about quantum entanglement, something entirely different from what you're talking about. Quantum entanglement's effect is basically the transfer of information at faster than light speeds (nonlocal). It has nothing to do with reconstructing particles from other particles at a distance.

But it's NOT teleporation. Teleportation involves taking an object from point A and moving it to point Z without crossing the in-between space, C through Y.

Teleportation of photons has been done in the lab, and you are correct that the method of doing this involves destroying the original particle to create the new one which is located spatially apart from the original. But the particle *is* crossing the in between space. The information required to reconstruct the carbon copy particle is transferred to the final location, in effect, transferring the actual object. Whether this is a nonlocal (entanglement type) effect or not makes no difference. If it's a nonlocal transfer, then true the particle doesn't 'appear' to actually travel through point B to get to point C, however in reality it *must* be travelling spatially otherwise your arguement would be that every point in space is physically connected to everything, in effect, everything in existance in the universe is condensed into an infintesimal point such as the singularity 'particle' that existed before the big bang.

Think of it this way, if every particle of your body, subatomic or otherwise, was teleported to another location using this method, and in the process the old particles were destroyed, would you not in effect have been teleported in the star-trek idea of the concept? This can bring in pretty deep philosophical arguements, but by looking at the problem with a deterministic, or classical viewpoint of consciousness, your brain, your 'self', should function in its new location just as it did in the old one.

Whether this is true, or whether you'd just be a hump of biochemical dead matter is a question left for those brave individuals (or unlucky animals) who will be the first ginea pigs in human teleportation devices.

Re:Not true teleportation

[nihilogos]

Quantum entanglement's effect is basically the transfer of information at faster than light speeds (nonlocal).

This is just simply not true. There is no transfer of information faster than light and there is no action at a distance. To 'teleport' a quantum state requires the transmission of classical information over a radio, email, tin can and string or whatever. Without this classical transmission we would have no correlation between the states whatsoever.

Re:Not true teleportation

[nihilogos]

I just read the article because, like you, the 10^12 atoms bit sounded phenomenal.

From J Cirac's (a.ka. God) review:

The trick is to have a superposition of two states: one in which slightly more than half of the atoms in each sample are spin up and another one in which slightly more than half are spin down. If the environment interacts with one or more atoms and 'observes' that it is spin up, this is compatible with both states so the superposition is not destroyed but slightly damaged. As a result trillions of atoms must interact with the environment before the entanglement disappears

This is kinda similar to the way we can have robust superpositions from population differences in NMR.

Another interesting part of the experiment was that they managed to entangle two samples which were physically separated with a single light beam. This is the first time non local entanglement has been generated.

All in all, since most quantum experiments are hard because of the fragility of the phenomena in our experimental domain this looks very interesting.

Re:Not true teleportation

[BRTB]

I was just about to say something about that book; great reading if anybody hasn't yet.

Of course, if I remember right (big IF there), the really scary part of their teleportation method was that even though they perfected the laser disintegration, fractal-compression and transmission processes, they had absolutely no idea how to reassemble the matter once the datastream reached its destination reality. Again they relied on the infinite-universes theory and knew that in one random quantum universe, their counterparts DID know how to reconstruct the matter and the source matter from THAT reality would get reconstructed instead - but not be different enough to change anything.

All of which has absolutely no relevance to the actual topic but I thought it was really cool. =]

Re:Not true teleportation

[chron]

There is no transfer of information faster than light and there is no action at a distance.

How do you define information? If particle b is affected immediately upon collapse of particle a, then how has an action not occured? We only must agree that particle a is seperate from particle b in space to make true that an action has occured, whose 'effect' has been transferred faster than light speed. Here effect replaces the word information.

What's actually being transferred here? If the effect itself is the change of quantum state then what mediates this? If both particles are spatially seperated, and one particle's quantum state is affected by a change in the other's change in state, then 1) a force must exist to mediate this change, and 2) this force must be travelling at faster than light speeds (hence being acausal, goes backward in time, etc).

The only way to escape this logic is to assert that particle a and particle b are not really seperated in space at all, but are physically connected somehow (through a wormhole perhaps?). This will be answered when general relativity and quantum mechanics are brought together in a cohesive theory.

Re:Not true teleportation

[DickBreath]

Nature is a peer reviewed journal

Well, Slashdot is peer reviewed too. So that should give it equal credibility.

So there.

Re:Not true teleportation

[nihilogos]

To make things a little more precise here lets suppose particles a and b are photons, and that we are measuring their spin polarisation which can be either horizontal H or vertical V.

If particle b is affected immediately upon collapse of particle a, then how has an action not occured?

Suppose we've got particle b and someone else on the other side of the solor system has particle a. If we measure our photon we are 50% likely to get an H, and 50% likely to get a V. This occurs whether or not (a) has measured their photon prior to us. In the absence of any communication from (a) we can determine no physical change in the photon whatsoever. Actions are something that effect physical changes and there are none here.

The EPR paradox is not a paradox at all. It does not require any resolution.

Re:Not true teleportation

[chron]

If we measure our photon we are 50% likely to get an H, and 50% likely to get a V. This occurs whether or not (a) has measured their photon prior to us.

This is false. If particle (a) has already been measured then the 50/50 probability disappears and we are guaranteed that we will get the opposite spin of particle (a).

However, when we measure on our side particle (b) we don't know that particle (a) has already been measured, or what the result was. But this does not change the fact that the outcome of the measurement is predetermined.

Re:Not true teleportation

[nihilogos]

This is false. If particle (a) has already been measured then the 50/50 probability disappears and
we are guaranteed that we will get the opposite spin of particle (a).

No, it isn't. In the absence of any communication from (a) we still have a 50% chance of getting an H, and a 50% chance of getting a V. We cannot detect any physical change in the photon, and not detecting any change is equivalent to there not being any change.

Look at it this way. If (a) had not told us anything about her measurement would you be willing to bet your entire fortune on the outcome of ours?

Re:Not true teleportation

[chron]

No, it isn't. In the absence of any communication from (a) we still have a 50% chance of getting an H, and a 50% chance of getting a V.

Yes this is correct from the *local* perspective where measurement (b) takes place, but in actuality the outcome of our measurement is predetermined by the measurement already done on particle (a). This is an experimentally verified fact, and why entanglement is such a big deal. There is a transfer of effect faster than light. Once particle (a) has been measured and collapsed, particle (b)'s measurement outcome is thus determined.

Look at it this way. If (a) had not told us anything about her measurement would you be willing to bet your entire fortune on the outcome of ours?

Of course not, but this has nothing to do with us trying to predict what the outcome will be on our side. The fact remains our measurement of particle (b) is predetermined to have the opposite outcome of the previous measurement of (a).

Having local knowledge of what this predetermed outcome is before we measure (b) is of course impossible. But you're mistaking this with the fact that the outcome of our measurement of (b) is determined by the previously collapsed wave of our entangled sister particle (a).

By the way, whats up with this auto-mod points for your posts?

Re:Not true teleportation

[nihilogos]

Yes this is correct from the *local* perspective where measurement (b) takes place

But this is the only perspective we have. There is no observer which can have a perspective at both (a) and (b) without the transfer of information between the two.

There is a transfer of effect faster than light

Once again note that, in the absence of communication from (a), we can't detect any physical difference in our photon. The only way we can say an effect has occured is if we can detect one.

By the way, whats up with this auto-mod points for your posts?

25+ karma. Mostly from inane comments that got modded +5 funny. Gotta run, my email is [dawson at physics dot uq dot edu dot au] if you'd like to reply :)

Re:Not true teleportation

[gdr]

But it's NOT teleporation. Teleportation involves taking an object from point A and moving it to point Z without crossing the in-between space, C through Y.

Then how do you know it's the same object and not a copy if you don't follow it through space from A to Z? What's the difference between destroying an object and creating an exact copy at another position and the object "traveling" between these points without existing between the points.

Re:Not true teleportation

[Anonymous Coward]

The problem with replicating a person and then destroying the original comes down to something *far* more complex. Are we just the sum of all our parts? If we aren't just some atoms glued together and there is something else (a soul), then replication and destruction of the original will fail.

Think about this: If I "teleport" you, then for a short while there are 2 of you. I destory the 1st one and the 2nd lives on in the destination - no-one can tell it apart from the original. Except that you died when I destroyed the 1st one, including your conciousness.
If you think about this hard enough you have to come to the conclusion that we are either not alive (i.e. not concious), or that we have a soul.

Chaz

Re:Not true teleportation

[chron]

Once again note that, in the absence of communication from (a), we can't detect any physical difference in our photon. The only way we can say an effect has occured is if we can detect one.

I agree that from perspective (b) one cannot detect the effect measurement (a) has already made on particle (b) until after you measure (b), but the paradox is that in fact (a) is already predetermined because a faster than light signal, transfer of effect, whatever you want to call it, has made its way through space from the point where the collapse of particle (a) takes place. Even though you don't have knowledge of it from any perspective, the effect still takes place, and the effect transfers at faster than light speed.

Better yet!

[SpanishInquisition]

Why not just teleport the whole thing directly into your stomach, that way you wouldn't have to taste the rotten meat and all the crap they put in there. And I'm pretty sure will be a cashless society when teleportation arrives.

Re:Better yet!

[geekoid]

even better, teleport the key particles right were your body needs them?good by fat.(which they could beam out of you if you want to take nitrients the 'old fashioned' way.

Re:Better yet!

[SpanishInquisition]

Ouch, cosmetic surgery by teleportation.
Hey teenagers could even get breast implants over the phone if they can steal their parents credit card.

Re:Better yet!

[silicon_synapse]

I don't know about that. With functional teleportaion and a little hacking, teens could probably swap breasts or other body parts. The questions is can you supply raw material and recreate an object if the pattern is still in the buffer or some other storage a la replication. I guess replication is just one step beyond teleportation. The next question is who owns the rights to your data as it's being transmitted? Do data streams have rights?

P.S. Don't you hate it when someone looks right past the humor and tries to answer you seriously?

Re:Better yet!

[Nyrath the nearly wi]

And I'm pretty sure will be a cashless society when teleportation arrives.

If it is not cashless when teleportation arrives, it will be afterwards.

In the classic SF novel VENUS EQUILATERAL by George O. Smith, the heros invent a matter transmitter.

Shortly afterwards they realize that it is also a matter duplicator, making perfect duplicate of whatever you put in the hopper. What's worse, they can make "recordings" of objects, and play them back to make duplicates.

Some clown starts selling matter duplicators to the general public, and the economy of the entire planet collapses. What good is a mink coat or a Lamburgini if everybody and his brother has one?

Not to mention the possibilites of counterfeiting money.

By the time things have sorted themselves out, money is obsolete and the economy is based on personal services (the doctor removes your appendix and you pay him back by mowing his lawn for a few years)

Our heros do help out things by creating a material that cannot be duplicated, for use as a material to write checks on, and so forth. (It is not so much that it cannot be duplicated so much that it explodes when the matter duplicator scans it)

implications of faster-than-light information

[Anonymous Coward]

So besides amazing quake games, what would a networking technology based on this give us?

Re:implications of faster-than-light information

[toddhisattva]

Etherlessnet

From the book about Milliways...

[Chris Brewer]

I teleported home one night,
With Ron and Sid and Meg,
Ron stole Meg's heart away,
And I got Sidney's leg.

Scientists observer quantum entanglement and

[scotch]

Scott Bakula returns to television tonight. Coincidence? Don't believe it.

Quantum Entanglement

[blitz77]

Quantum entanglement is basically splitting up a photon into 2 parts. These 2 parts are quantumly entangled, so when you measure one, you would get exactly the same result on the other as a result of them being entangled. The supposed ability to transport particles is not true. It is only able to allow measurements on one particle to be duplicated on the other. So, if we ever get this to work on large objects such as humans (!) you wont get teleported. There'd only be a duplicate of you on the other side. And in the act of measuring the state of all the particles of your body, you'd probably be dead too. I wouldnt care to have a duplicate of me on the other side, because you'd still be dead.

Re:Quantum Entanglement

[DanEsparza]

You're funny.

While I would agree that this is the classic explanation of this phenomena I think it's important to point out that the photons can't be observed directly (like under a microscope) -- and we honestly don't know what the heck is going on at this point.

The article points out Einsteins famous quote describing this phenomena is "spooky action at a distance" -- which it is. I'm sure if you asked Schroedinger (spelling?) he'd tell you that the photon 'was neither split, nor one photon' ... because we just don't know.

If you want an interesting (although hardly scientific) read on this subject, check out Michael Chricton's 'Timeline' book.

Re:Quantum Entanglement

[dragons_flight]

A) While isolating different parts of a particle's wave function is possible, this is rarely, if ever, what is meant by entanglement. Typically what is meant involves bringing multiple particles together and getting their wavefunctions to operate as a coherent entity, and maintaining this "coherence" after seperating the particles.

B) The measurement doesn't have to be the same (in fact quite often they respond by giving exactly opposite measurements). The only requirement is that they behave in a well defined correlated way predicted by Quantum Mechanics.

C) You are thinking of "fascimile copying" which is different from teleportation. In the first case you exchange information through entangled particles to create a close (but never perfect) duplicate of the original. In teleportation you destroy the state of the original to create an exact duplicate at the other end. This reference provides a good explanation of the ideas behind teleportation.

D) Yes, you would have to entangle your whole body in order to teleport, but there are plenty of nondestructive ways to measure the body (think X-Rays), and it doesn't neccesarily follow that in some distant future there won't be a way to preserve at least one intact copy.

Re:Quantum Entanglement

[Anonymous Coward]

ROFL

X rays as harmless.

ROFL

Retard.

And if you think using an x-ray to generate the required information every particle will work, you're even more retarded. The censors used to test these experiments need serious proximity.

Re:Quantum Entanglement

[sigwinch]

D) Yes, you would have to entangle your whole body in order to teleport, but there are plenty of nondestructive ways to measure the body (think X-Rays),

BWAHAHAHAHAHAHAHA! Do you have any idea of the power density of a one X-ray photon per nucleon beam? Hint: it'd probably make a supernova look dim. Nondestructive? <snort>

Re:Quantum Entanglement

[dragons_flight]

X-Rays are just an example of a way of measuring the interior without taking the body apart to do it. I fully agree they wouldn't serve for teleportation, but hundreds of years from now there may be ways to selectively interact with the interior without any destructive consequences.

Re:Quantum Entanglement

[aozilla]

I fully agree they wouldn't serve for teleportation, but hundreds of years from now there may be ways to selectively interact with the interior without any destructive consequences.

Umm, wouldn't that violate the Heisenberg Uncertainty Principle?

Re:Quantum Entanglement

[dragons_flight]

No.

Entanglement and Measurement (as defined in Quantum) are mutually exclusive propositions. Measurement deals with wave function collapse to select a particular pure state. Heisenberg Uncertainty Principle limits what measured states are allowed to coexist simultaneously. Entanglement deals with the mixing of states across across different particles. Measurement destroys entangled states and entanglement can not exist solely based pure "measured" states.

In other words since we are dealing with entanglement to create teleportation, Heisenberg's principle doesn't apply, as it only deals with measured (ie. not entangled) states.

Ansible

[mmmmbeer]

I don't see how this would allow for teleportation. As many others have already mentioned, how do you draw a link between this and the ability to transport (or even duplicate) matter?

However, I do see a possibly very significant use of this technology. If you can maintain an entangled state between macroscopic objects, wouldn't this allow a change to one object to be seen immediately in the other? If so, couldn't this be used to create computer networking devices which would work over any distance without any delay, and without any necessary wires or similar infrastructure? This sounds like it could potentially create the "ansible" predicted by Ursula K. Le Guin and Orson Scott Card.

Re:Ansible

[uchian]

Great, does that mean I'd get decent pings when playing Counterstrike on an American server (I'm in the UK)?

Re:Ansible

[Winged Cat]

Teleportation of information, not teleportation of matter itself. You're right, the matter still has to get to its destination by standard processes. You'd need something like nanotech assemblers and scanners for teleportation:

1. Get a bunch of raw materials, and a teleport receiver, to the teleport-to site.
2. At the teleport-from site, scan the object to be "teleported" at an atomic (or maybe subatomic) level, possibly destroying it in the process.
3. During the scan, transmit the scan's results to the teleport-to site, assembling a duplicate of the teleported object.

Re:Ansible

[Anonymous Coward]

You still cannot pass any information faster than light this way. Your problem is that a particle has an indefinite state before a measurement is conducted. Since you measure something, say the spin, the spin becomes defined once you measure it. Still you need to know when to determine the spin and this information you do not have and your measuring is going to affect the result. In short, no Tomorrows Slashdot News Yesterday, sorry.

Re:Ansible

[huh_]

This site has a pretty good explanation of quantum teleportation. It also shows why there would not be a duplicate copy of something that is teleported because it destroys the state of the original automatically.

Re:Ansible

[MobyDisk]

I thought that transporting information superluminally violated causality. Remember this article about superliminal transmission of microwaves in a cesium gas? It sparked a discussion about how useful this would be for data transmission. But I understand that the general scientific opinion is that causality prevents this from actually being able to send information faster than light. The same thing happens with gravity. Gravity doesn't travel truly "instantly" in all frames of reference, so you cannot transmit information faster than light by adjusting mass.

If someone could clarify this it would be great.

Re:Ansible

[QuantumFTL]

I've read sections of Card's book How to Write Science Fiction that I got for my younger brother. In there he explains that the ansible is a complete an utter fictional device, which knowingly violates the laws of physics. He used it as a plot device, and tried to make it at least somewhat credible. Study relativity, you'll understand why FTL makes no sense. If you have FTL communication, cause and effect is no longer preserved from every possible inertial reference frame.

Also, note, that the information that's transferred means absolutely nothing until it's decoded by classical signals.

This is not, however, to say that this communication is not useful. In the fields of quatum computing, this could be used to link distant processors together.

IANAP (but I hope to be one some day, after I finish up my bachelors here at Cornell) but I follow this stuff intently. Hope this clears up something.

Re:Ansible

[aozilla]

Still you need to know when to determine the spin and this information you do not have...

1. Synchronize atomic clocks
   
2. Person A travels in one direction
   
3. Person B travels in the opposite direction
   
4. Clocks are still synchronized
   

Re:Ansible

[Anonymous Coward]

I thought that transporting information superluminally violated causality

Yep, that's the current theory. But it's always possible that Einstein was just plain old wrong, and that Lorentz was more correct. Neither theory has been disproven.

Re:Ansible

[mmmmbeer]

I understand what you're saying, but I still don't think it applies to this technology. After all, you could do the same thing with any other means of data transfer.

Re:Ansible

[mmmmbeer]

Why couldn't you just scan constantly? It'd be no different from how your modem works. When you see the signal start switching between zero and one, you know a signal is coming through. As long as you're ready for a signal, you shouldn't have to know exactly when to expect it.

Re:Ansible

[Winged Cat]

True. It helps with the bandwidth, but it's not essential. Like I said, it's "teleportation of information", which some people generalize to just "teleportation" (including of matter).

Re:Ansible

[William Tanksley]

I can't clarify this one, but I can perhaps shed a little light on the cesium experiment. No pun intended.

It didn't involve FTL transmission. Not at all. What happened was that they observed a wavefront travelling FTL. Wavefronts aren't information by themselves; they're merely the conincidental addition of light waves of different wavelengths.

For a concrete demonstration of this, together with a better explanation than I could ever give, please point your Java-enabled browser at this page.

-Billy

Tron?

[sharkey]

Sounds like the matter transferance laser in Tron. Don't sit in front of it and piss off the computer.

MCP: Back again. Flynn?
Flynn: Well, well, well, if it isn't the Master Control Program.
MCP: You know I can't allow this, Flynn.
...

Re:Tron?

[Anonymous Coward]

Flynn: What's it like being a program?

Tron: You just go on doing what you think you're supposed to be doing, no matter how crazy it seems.

Flynn: Sorry to break it to you, pal. That's the way it is for users too.

Re:Tron?

[Anonymous Coward]

I'm continually amazed that tron and troff never got into an argument.

Really?

[Liquor]

The article has such an astounding lack of detail that it makes me wonder if this is another case of Yahoo News hacked to provide a story.

How did they determine that there was any quantum entanglement? Once you've got enough atoms, the average properties of both are going to be the same anyway :)

For that matter, what was the setup? And how come the slashdot article says the report is in 'Nature', but the link takes you to Yahoo?

Re:Really?

[Liquor]

Ok, following myself up here, the link to 'Nature' is the link to the article, and the link to 'reports' is on Yahoo.

So I didn't look at both of them. :(

But even the Nature front page is vague (and I can't access the full article) - though it does add the information that there are two cesium gas samples - similar to that in a cesium clock? - that were entangled, but my comment about how did they determine there was entanglement still stands. There needs to be more information before I can even tell if this was anything more than a two-cavity laser effect.

PLEASE, save our brains-- we need your help....

[Anonymous Coward]

The article on yahoo was about the worst science writeup I've ever seen. This is an interesting report, but it appears that you may actually need a print subscription to access all of Nature's online content. Can someone provide a mirror of the article, or a good bit copy/pasted? All yahoo had to say was that some day real soon we'll be zipping back and forth in teleporters using this magical force called "science".

Aww...

[kypper]

The effect, called quantum entanglement, has been observed before, but never with such large amounts of matter. Don't expect transporters next week...

Jeez... so I have to take the bus to school again??? Bloody hell, where are my taxes going?

I heard of this before, except it was actually the concept of destroying the original and rebuilding the particles at the end-point. Wouldn't cloning take on an interesting point there?

This uses entanglement tho. Can anyone explain it in layman's terms?

Quantum Computing

[cailloux]

One real posiblity for quantum entanglement would be in the area of quantum computing and distributed processing. The theory in a quantum computer is that every possible state of every computation can exist simultaneously. Only after you decide you want to know the answer to a specific problem will you find it - in effect any complex calculation is speeded up my magnitudes of order. In a distributed environment, quantum entanglement would allow for 2 (or more) quantum computers to join together and each work on a distributed/parallel process program and instantly share data, as well as solutions. For example, in gene research the refinement of proteins into useful medications could take place at a much faster rate because each quantum computer could "see" what the other got for evolutionary results and apply those changes along separate lines of reasoning while still being aware of what worked and what did not.

In a non-quantum computing environment, data networking could happen much faster (blowing the doors of gigabit ethernet) by being able to instantly transfer the entire contents of a hard drive from one place to the next along fiber; no longer are you sending electrons at high speed (c), but now you are transferring the entire data packet straight from one network card to the next.

-cailloux

Re:Quantum Computing

[Anonymous Coward]

In a non-quantum computing environment, data networking could happen much faster (blowing the doors of gigabit ethernet)

gigabit refers to the bandwidth, not the latency. Presumably this method would still have a limited bandwidth, but it would have no latency. Of course that alone would tear apart just about everything einstein said about special relativity.

no longer are you sending electrons at high speed

In reality the actual electrons move very slow. What you have is more of an electron relay system, where one electron moves slightly which causes the next electron to move slightly, and so on down the chain. Photons are what move fast.

but now you are transferring the entire data packet straight from one network card to the next.

Again you seem to be confusing bandwidth and latency...

explanation of teleportation

[lkcl]

Re: clarification here is an explanation of teleportation [posted as another part of this thread].

Re:Not true, B

[charon_on_acheron]

I just figured he opened up his "My Computer" icon, saw Drives A:, C:, D:, E:, F:, etc:, and decided that the letter B stopped existing when the single-floppy PC was introduced.

A Clarification...

[HEbGb]

Clarification:

Quantum entanglement involves creating a system in which the state (polarization, spin, etc.) of two or more particles are 'dependent on' each other. Measuring the state of one particle defines the state of the other, 'magically', over some distance.

HOWEVER make no mistake, nothing in quantum mechanics or entanglement theory allows anything resembling faster-than-light information traveling, nor teleportation as we understand it. This is pure fantasy that many physicists subtly or not-so-subtly use to solicit grants, or at least popular press. (There's plenty of this nonsense in sci-tech magazines.) It certainly worked here.

Here's another example of macroscopic 'quantum entanglement'. I have a bag with two billiard balls, one black, one white. I close my eyes, pull one out and put it in a second bag. Then, I hand you the first bag, and walk across the room with the second bag, and open it. Once I look at the color of the billiard ball in my bag, the color of the ball in your bag 'magically' changes color and assumes a defined state. These billiard balls are entangled, very much like subatomic particles are.

Can you ever transport information faster than light using this method? NO. Can matter be teleported? NO. I really wish these pop-sci articles would put an end to these misconceptions once and for all...

Re:A Clarification...

[jaoswald]

It doesn't necessarily "change the state" of the second particle. (It can't, since the particles cannot causally interact; the particle's state evolves according to the local environment). However, the results of measurements on the second particle are inter-dependent with the results of the measurements of the first particle, even though the acts of measurement themselves cannot be connected causally (in the sense of special relativity).

The really funky thing is that the *choice* made to determine what kind of measurement to make on the first particle affects the inter-dependence. The idea being that "somehow" the measurement apparatus is communicating its setup to the distant particle, even though it really can't. This is really disturbing, but probably doesn't have any better explanation than "that's just how it is."

Re:A Clarification...

[renard]

Your billiard ball example is equivalent to Einstein's "hidden variables" attempt to explain away quantum entanglement. Bell's theorem demonstrated that the predictions of quantum mechanics were actually inconsistent with such a theory - and subsequent experiments proved him right. The universe is far more mysterious than you or Einstein give it credit for.

In fact the reproduction of a quantum state - in all its particulars - is as perfect a teleportation as we might ever expect to achieve - see my accompanying comment. So I don't think your criticisms are entirely justified.

I say "not entirely" because extrapolating 13 orders of magnitude, and to real systems rather than super-cooled ones - as required for useful teleportation - still requires a bit of hutzpah. But the scientists cannot take all the blame. After all, the Trekkies were there long before...

-Renard

Re:A Clarification...

[pongo000]

Your clarification is only partially correct. Under some very limited conditions, superluminal (faster-than-light) speeds are possible. I remember reading about this in The Dancing Wu Li Masters (very good overview of relativity for the non-physics types out there). A quick search for "superluminal" in your favorite search engine will generate links such as this Scientific American article about the very limited conditions necessary for superluminal speeds.

Re:A Clarification...

[Rothfuss]

Your billiard ball experiment is an interesting little analogy, but shows a lack of understanding of true entanglement.

Quantum entangled states behave as unknowns from the time of entanglement and remain "unknown states" until a measurement is made. Even though you haven't looked in the bag, physically the ball *is* either black or white and has been all along. Your knowledge of it's state doesn't matter. It is definitely in one state or the other, regardless of your own knowledge of the matter.

On the other hand, the quantum entangled particles are *not* actually in a state until a measurement is made which collapses the wave packet and by various conservation reduces both particles/photons/whatever to their correct state.

If you are thinking "Well it was really just that way all along," you are fundamentally missing the coolness of Quantum Physics.

-Rothfuss

Re:A Clarification...

[vinylat33]

nothing in quantum mechanics or entanglement theory allows anything resembling faster-than-light information traveling

That is correct. However, a particle (or any other exitation in a quantumfield) may only exist when there is a solution.This solution may be over time.

example: light you see from the sun (a photon traveling from emission of the sun to absorption in your eye) only exists because it is a solution in the quantumfield. Hence it is impossible to duck for that photon, cause it would never exist if you were not there.

The problem this article, i think, is about changing states of a symmetry broken system. Symmetry broken systems are like superconductivity, but also simply said a table. Depending on the system.
I have to read the insights, but i think it is not so new as they postulate.
In fermi-systems, like liquid 3He, at temperatures below its fermi-temperature, the whole system is in *one* state, which cannot be changed with low energy, cause you have to change the whole system. Maybe this is about a change at low energies than the system.

or maybe i am bullshitting.

Re:A Clarification...

[Anonymous Coward]

Can you ever transport information faster than light using this method? NO

Has it been *definitely* proven that we cannot and will never be able to? Or is it a case of "we currently don't know how to and it seems *unlikely* that it is possible"? Two very different situations of course. I'm interested to know which it is, because if its the latter, then there may still be some way to do it, and that physicists just don't know how to now because its beyond our current understanding of physics.

Re:A Clarification...

[sigwinch]

Your billiard ball example is equivalent to Einstein's "hidden variables" attempt to explain away quantum entanglement. Bell's theorem demonstrated that the predictions of quantum mechanics were actually inconsistent with such a theory - and subsequent experiments proved him right.

Bell's theorem only disproves *local* hidden variable theories, of which the billard balls are an example. (On the other hand, the billiard balls are a good example for the nonspecialist who wants to comprehend the effects without breaking their mind against quantum nonlocality.) Nonlocal hidden variables are perfectly allowable by the Bell inequality (and indeed I think they have considerable merit).

In fact the reproduction of a quantum state - in all its particulars - is as perfect a teleportation as we might ever expect to achieve...

In my opinion it doesn't count as teleportation. The systems were too homogenous and contrived. When they can do it for condensed matter containing multiple elements, I'll be willing to consider it teleportation.

Re:A Clarification...

[Anonymous Coward]

For two states, yes ... your example does not illustrate, but in fact trashes the entanglement concept! But not for a 3-state system !!! That is, if each of the two balls could be any-of-three colors. See Penrose among many for truly baffling discussions of the Bell inequalities ... whips my azz.

Re:A Clarification...

[caffeinated_bunsen]

The faster-than-light seeming aspect of it appears disturbing at first. But after a while, you realize that it occurs anywhere in quantum mechanics when a wave function collapses.

Think about it. Consider 2 polarized photons, 2 electron spins, 2 billiard balls, anything entangled such that a particular measurement performed on each always returns opposite results. When the system is set up, each object's probability of being, say, spin up, is 50%. The two spins are described by coupled wave functions, so that the 50% that corresponds to A being spin up also corresponds to B being spin down and vice versa. When one is measured, its wave function collapses into a single eigenstate, and its partner's wave function collapses into the other eigenstate. Thus, the final eigenstate of B is decided by the same measurement that measures the state of A.

This seems disturbing, the instantaneous change of B's wave function an arbitrary distance from A, when only A is being measured. But the simultaneous collapse of 2 coupled wave functions is mathematically no different from the collapse of a single wave function. When you have a particle with a large uncertainty in position, mesuring its position causes it to collapse to a single position eigenstate. If you have 2 detectors some distance apart, and use each to measure the presence or absence of the particle some very short time apart, you know that if you observe it at one, you won't observe it at the other. Say the detectors are 10m apart, and they take their measurements 1ns apart. If you detect the particle at the first one, you KNOW that the second won't detect it. But the 'information' about the wave function's collapse at the first detector would take 33ns to reach the second, if it travelled at the speed of light. So a single wavefunction's instantaneous collapse from all of space to a single point is just as much 'communication' as an entangled particle pair's simultaneous collapse.

So you have a choice: Either the entangled particles' behavior isn't that disturbing, any measurement of a quantum system is really disturbing.

Re:A Clarification...

[Rothfuss]

It is generally accepted that it *has* been proven that you can't go faster than the speed of light. The "exceptions" that have been noted above are light travelling faster than the speed-of-light-in-a-vacuum under special conditions, but nothing else will travel faster than it under those special conditions.

The cool thing that most don't really realize is that the same equations that tell us we can't go faster than light also tell us that by going very near the speed of light we can cover incredible distances in extremely short times due to the length contraction associated with such high velocities with respect to an inertial frame. If the inertial frame is taken as the center of the galaxy for example, and your body is accelerated radially to 0.9999c (please don't ask how), it will perceive distances with respect to the galactic center inertial frame as being about 1/100th what they are perceived as being in the galactic reference frame. So you are effectively traveling at 100 times the speed of light even though light is still moving at the speed of light in your inertial frame as well as the galactic frame (frequency is shifted). From the perspective of a man at the center of the galaxy you are moving at 0.9999c and your trip to a location 100 light years away will take a little over 100 years as he sees it. To you it will take about 1.5 years.

That's special relativity, and it is the last bit that is responsible for the infamous twin paradox.

And just to be particular on this, the key to all of it is in the acceleration, not the velocity.

-Rothfuss

Re:A Clarification...

[Kynde]

Quantum entanglement involves creating a system in which the state (polarization, spin, etc.) of two or more particles are 'dependent on' each other. Measuring the state of one particle defines the state of the other, 'magically', over some distance.

HOWEVER make no mistake, nothing in quantum mechanics or entanglement theory allows anything resembling faster-than-light information traveling, nor teleportation as we understand it.

The difference between a person who reads popular science magazines and actually studies/researches in the field of quantum physics is that the magazine reader tries to understand QM whereas the scientist-like lad knows that it's futile. In the words of one of _the_ lads in QM, Richard P. Feynman : "I feel I can safely say no one understands quantum mechanics"

These non-local effects (locality as in limited by the speed of light) of quantum theory is the biggest concern usually. And to be frank not just because it's fruitfull soil for science fiction, but also because it contradicts theory of relativity. ToR clearly states that not only causality cannot be broken but also that non-local variables cannot exist, which in other words mean that any interaction or information exceed the speed of light. Well, in quantum mechanics non-locality is present, moreover these non-local effects have been verified to exist. This entanglement is an example such effect, another is how tunneling can cause light to pass through solids faster than the speed of light, and many others. (this contradiction is often called as dualism in the field of physics and it's been present since the early 20th century, and still is. GUTs are approaches to unify these theories. The problem with the is that their predictions mostly fall out of our measurement scope.

So what of it, is theory of relativity faulty or what. That sort of remains to be seen. Both theories have proven to be remarkably successfull in their predictions in their domain, but obviously the model that they give is not complete enough. Newton wasn't "wrong" with his gravitation, it merely refined with a more accurate version.

Re:A Clarification...

[Jace of Fuse!]

If you are thinking "Well it was really just that way all along," you are fundamentally missing the coolness of Quantum Physics.

Or, if you are like some dimwits I know, you say "It was really just that way all along, there is no such thing as Quantum Physics, and the only people who believe in it are Scientists who want desperately to believe in god."

I hate that argument against Quantum Phyics.

It's apparently very hard for people that are supposedly "so smart" to admit just once that they don't really know a damned thing. It's almost as if they fear the ever important concept that everything they know is wrong!

Re:A Clarification...

[hickmott]

This would be a slightly better analogy. It's still an analogy and so false to fact, but it captures quantum entanglement a little better.

You have a sack with two balls in it, one weighing 10kg, one 100kg. You and your friend each weigh 100kg. You and your friend each take a ball without looking at it or noticing its weight. (Don't ask how, just do it.) You walk to opposite ends of the room, each passing over a scale that rings an alarm if 175kg passes over it. Neither alarm rings. You open the bags and find one 10kg weight and one 100kg weight.

Until you open the bags and check the weights, the bags contain an odd, entangled combination of the two weights.

Re:A Clarification...

[BeBoxer]

Are there any good books accessable to a layman which explain Bell's theorem and the associated experiements? I've never understood why people insist that there can't be a hidden variable, when it is far and away the simplest explanation for these phenomenon.

Re:A Clarification...

[HiThere]

This kind of problem is one of the reasons that I prefer the multi-world interpretation.

Consider: A star emits a photon. Years later, the photon is spread out over an area of several square light years. Eventually it may be detected. Say by Hubble. Once Hubble has detected it, it should not be detectable elsewhere in the universe that occurs within Hubble's forward light cone. But at about the same time (more or less.. can't be too specific here) it is detected by an alien probe circling Sirius B. In some frames of reference the encounter a Sirius B happened first. In others the encounter with Hubble happened first. But they shouldn't both happend in the same universe. So the interpretation that I favor is that the universe split when the state function "collapsed". I.e., the collapse of the state vector is a method for enabling calculations to only cover the futures that we might encounter.

Now let's think about this "teleportation" thing. Until you "look in the box" the state of the system is mixed. Once you look, you immediately know which universe you have ended up in. You may have also ended up in other universes, but this you will never encounter them in your traversal of your forward light cone. Since you know which universe you are in, you know that, barring other unexpected factors, the state of the system that you have observed is correlated with the state of the system that you didn't observe. Where they are located doesn't have anything to do with this. They could be at Sirius B and it wouldn't matter. What matters is that they haven't been disturbed since the correlation was created.

The problem is that the guy who carried them to Sirius B might also have peeked. And when he comes home, his answer will agree with yours. And you won't really be able to tell which peeked first. Really. But this is because the you that peeked and the him that peeked ended up in the same universe (or you couldn't have encountered him).
In another, equally probably universe, you discovered a different answer when you looked. But so did he. So when you compare notes, you still get agreement.

You can think of this as a non-local variable, if multiple worlds distresses you. It gives exactly the same predictions. But I find global variables hard to justify, and use as few of them as possible in my explanations (and code). But just consider how many global variables you are asking the universe to contain.

The possible stories to explain quantum physics seems to be limited to about five. Perhaps fewer, perhaps more, it's hard to know. They are all strictly constrained as to what predictions they are making, and are basically questions about what mental imagery one will use to think about it.
1) Solipsism: The universe is the creation of my mind, and these are the laws of how my mind works.
2) Multiple-worlds. The universe is constantly splitting.
3) Non-local variables. The universe contains this one humongous block of global variables that determines pretty much everything.
4) Determinism: There isn't a knowable cause for everything, but the master plan of the universe specified how everything would happen even "before" the universe was created. ("before" is in quotes, as time is a part of the universe. If you can explaine where this plan resides ... well there are problems with all of these stories.)
5) Everything depends on everything else. The universe is a complex spring, with springs acting bi-directionally and through time as well as through space. Actually, this is my second favorite choice. Consider, in the frame of reference of a photon, how long does it take a photon to get from here to there? So light could be a sort of instantaneous spring. Distance wouldn't exist in the frame of refence of a moving photon. So light would be a release at one end balanced simulatneously by an acceptance at the other. And time wouldn't enter into it. Wonder how gravity would fit into this? The universe as a tensegrity construct?

Re:A Clarification...

[HiThere]

I found The Dancing Wu Li Masters to be more opaque than The Tao of Physics , but both rather ... they explain about as much as a Zen Koan. I understand why, or at least some of the reasons, but don't take them too seriously. They only make sense in the context of many other explanations, and a bit of work with the equations. Until then ... they will lead to many wrong conclusions, and the illusion of understanding.

The essential points are:
1) some things can't be known until you look, and
2) the universe ends up consistent.

Nearly everything else is an elaboration on that.

Re:A Clarification...

[renard]

Just looking around on the web (see this Google directory), I found a description of Bell's Theorem which is quite well done.

I can't think of any similarly superior book treatments at the moment but I'll check my bookshelves and get back to you if I find something.

-Renard

Re:A Clarification...

[greenrd]

The idea being that "somehow" the measurement apparatus is communicating its setup to the distant particle, even though it really can't. This is really disturbing, but probably doesn't have any better explanation than "that's just how it is."

No, I think this paper by Prof. David Deutsch (expert on quantum computing) gives a better explanation:

All information in quantum systems is, notwithstanding Bell's theorem, localised. Measuring or otherwise interacting with a quantum system S has no effect [my emphasis] on distant systems from which S is dynamically isolated, even if they are entangled with S. Using the Heisenberg picture to analyse quantum information processing makes this locality explicit, and reveals that under some circumstances (in particular, in Einstein-Podolski-Rosen experiments and in quantum teleportation) quantum information is transmitted through 'classical' (i.e. decoherent) information channels.

Re:A Clarification...

[penguinicide]

Actually ftl communications is possible. The problem is this. Once the 2 particles are entangled, they must be stored in separate devices. The devices must be separated over a measurably long distance. Now you can gain the benefits of ftl communication. With non-destructive modification/measurements of the particles (which happens instantaneously) you can transmit bits. The rest should be elementary.

Admittedly, alot of science has to be created to support such an application, but it will happen.

What i'm waiting for is a method of entangling 2 particles that don't happen to be anywhere near each other. That will enable all sorts of dangerous things.

Re:A Clarification...

[jaoswald]

You are right, of course, but you've simply wrapped all the strangeness up into a vaguely definable "collapse" of the wavefunction. Which I feel favors the latter statement.

This collapse can't really be treated rigorously, because the Schroedinger equation that evolves the wavefunction either has a simple Hamiltonian (the system) which causes linear time evolution (i.e. can't collapse, just rotate in state space), or includes a coupling to a vaguely defined "macroscopic" system which is not in a coherent quantum state. The interaction terms are what give rise to the "collapse" of the components that refer to the microscopic system.

Unfortunately, there is no way to really figure out physically where the incoherence of the big system came from. The incoherence is really more a statement either about ignorance of the true quantum state, which is a cop-out, because then you've forced a collapse on a state that is actually not going to collapse, or about the limitations of being able to set up a macroscopic system in a pure state, because you are at finite temperature, and don't have 10^100 years or whatever to prepare the system carefully enough to resolve the quantum levels of the system. I find this thermodynamic argument persuasive (i.e. it is really what happens), but still philosophically unsatisfying (i.e. it really doesn't physically explain where the thermal disorder comes from, if the universe as a whole is a quantum mechanical system.)

My personal opinion is that there isn't really any great philosophy that can be discovered by thinking about this much harder.

Re:A Clarification...

[jaoswald]

Hmmm. Very interesting.

Still, although I've only read the paper for maybe 10 minutes, it's not reassuring to find that the explanation depends on understanding:

"In other words, the information about theta, though present in Q2, is not detectable by measurements on Q2 alone."

I have a feeling I'm going to have a hard time understanding what he means by such "locally inaccessible information."

Thanks for the pointer.

Old news

[dickDragon]

This was presented at the

International Conference on Quantum Information
June 10-13, 2001 at the University of Rochester campus in Rochester, New York.

Re:Old news

[aka-ed]

*Very* informative link, particularly in its realistic assessment of what technologies stand to benefit from quantum communications. Anyone as confused as I was by the contradictory posts in this thread should checkit out...

anti-teleportation shields

[Sebastopol]

someone better get their ass in gear and invent an anti-teleportation shield pretty damned quick, otherwise terrorists will just be able to teleport bombs into buildings from anywhere.

maybe something involving large tanks of hot tea... or no tea... or both...

Re:anti-teleportation shields

[Anonymous Coward]

heh ... much easier to just teleport an extremely thin diagonal slice of material out of the structure ... Cut the building in half at an angle. Gravity finishes the job.

Uncontrolled teleportation technology would most likely result in the end of civilization as we know it. Want to kill someone? Teleport an air bubble into their body ... it travels through the bloodstream, reaches the heart ... boom. Want to rob a bank? Trivial.

I'll believe it...

[grammar fascist]

...when I can play Quake IX with my buddy on Mars at LAN speeds.

Still a big jump to teleportation

[Glorat]

As I understand Quantum Entanglement, you're not going to get teleportation with this. To create the initial entanglement, you have to perform an operation (such as shooting electrons with energy) to a pair of particles that are at the same inital location. The point of quantum entanglement is that once these particles are separated, the two particles still have this quantum connection between them.

But to get any transportation, you would need to put still need to transport(=move) one of those particles to the new location defeating the point of our transporter!

Re:Still a big jump to teleportation

[TeknoHog]

#include <IAAP.h>

It is enough to have pairs of generic particles that are entangled. These can then be used to transfer the quantum wavefunction of, say, James Tiberius from that one place to the other. In addition you need a conventional information transfer link between the places. The important implications are:

1. You cannot beam faster than light.
2. The original quantum wavefunction is destroyed by the quantum measurement -> no cloning.

Technobabble

[ahde]

It either proves Star Trek jargon is real or that this report (along with most "science" on slashdot these days) is baloney)

The most likely application

[btellier]

You're not teleporting matter, you're teleporting INFORMATION about the state of the movement of the particles at point A. From what I've read the first real world application of this would be something akin to the modems and NICs of today. The main benefits of course being that the transfer happens instantaneously and since trillions of atoms can be jostled at the same time, one could send as much information as the recieving end could sort through.

Re:The most likely application

[sheetsda]

The main benefits of course being that the transfer happens instantaneously and since trillions of atoms can be jostled at the same time, one could send as much information as the recieving end could sort through.

Not only that, but would it even be possible intercept the communication? Quantum packet sniffers anyone? And consider applying this technology to the current internet: once you establish a connection with a remote machine, no more data has to flow through the intermediaries which allowed you to find that machine (which clears up a host of other hacks/attacks).

Twinning

[Inthewire]

I've long thought that quantum entanglements may have something to do with the impressive ability of many twins to feel what their twin is doing...shoot, it isn't that hard to believe that some of the source matter for the embyos was in an entangled state and thus incorporated into the growing fetus.
I don't have any firm views on this...just wanted to throw it out there.

Re:Twinning

[Thing 1]

I've long thought that quantum entanglements may have something to do with the impressive ability of many twins to feel what their twin is doing...

Yes, and the anecdotal evidence that many mothers know when their children are in danger -- yet I have not once heard of a father knowing the same thing.

Entaglement in the womb. Perhaps we evolved wombs solely to gain the benefits of entanglement-based communications from brain to brain?

I have a somewhat longer post, here , on how I got telepathy out of quantum entanglement and the way the brain works.

yes, true teleportation

[Guignol]

But what is an object ?
Is an object what it is made of ? (ie. the information of the object is the object) or is the object what it is itself ?
Does every single particle have an unknowable divine ID ?
If the object is completely described by its composition, then yeah teleportation might be possible, because it is directly related to the exchange of information.
But, for what I understand, the information exchange itself isn't specialy fast, you comunicate an experiment result by a normal mean.
The good thing is, you don't have to destroy any copy, the process involves destruction itself (of the original, and in fact, before the reconstruction).
You have a pair of entangled particles, A and B, as far away as you want them to be. you want to send a quantum state Q information from where A is, to where B is. incertainty priciple states that you cannot do this measurement without affecting the information itself, but, what you can do, is measure it against A (scrambling A and Q which is the destruction part you can't avoid). the result of this measure of Q against A can be transported anyway you like to B, and applied to it reconstructing the original Q state. it's like a XOR operation :)

Science Rawks!

[Anonymous Coward]

...now if I could just make a half man, half monkey type creature, I'd be all set. I want my monkey-man!

Use the source...

[Anonymous Coward]

The homepage:
http://www.dfi.aau.dk/amo/qoptics/qoptics.htm

Direct links, that looked related:
http://www.dfi.aau.dk/amo/qoptics/qa.htm
http://www.dfi.aau.dk/amo/qoptics/
http://www.dfi.aau.dk/amo/qoptics/title.html

That's not a troll...

[NitsujTPU]

Dude, I love NASA and the space program, but don't you think that low latency high bandwidth point to point communications to mars would kick ass majorly? Toss up a router on mars and go to town? Come on, this would kill a big obstacle!

Re:That's not a troll...

[Anonymous Coward]

There is a project to put up a roughly T-1 throughput capable link from Earth to Mars running IP. 10 minute ping times would suck though.

Allows robotic probes to be controlled from Earth

[Anonymous Coward]

No need to send humans around, or to worry about hibernation. Instead send a probe with really good sensors on it. Then use virtual reality to let an "astronaut" here on earth to explore the planetoid. Neat!

Are we really this smart?

[MajesticFiles]

The potentials, of course, are staggering, but I have one question. Should the ability to teleport/transport matter between two points become reality, what of that vaporous non-matter that is so imporant? Our memories, our knowledge, all that is us? How do you transport something like that? Even if it's a duplication and not a true teleportation, how do you duplicate something like that? Wouldn't we just be transporting empty shells...the skin and bones and blood...but not the soul?

In anycase I guess my commute won't be shortened anytime soon.

Re:Are we really this smart?

[dragons_flight]

Well if you believe that it's all just electrochemical and/or quantum mechanical processes going on in the brain, then there is no fundemental problem with taking all of that along for the ride.

Judging from your post, I'll assume that you believe memories, knowledge, and "soul" don't result merely from complex physical processes. Fine, then point out where and what the soul is and precisely how it does relate to the brain, and I'll get right to work figuring out whether we can teleport it.

Thus far I've seen no evidence that anything happens in the brain which can't be explained by physical laws and processes.

Re:Are we really this smart?

[dangermouse]

... and we've seen no real evidence that everything that makes up a mind does exist as a chemical/electrical state in the brain.

What would be interesting is teleporting someone as a means of finding out.

Re:Are we really this smart?

[alexrios]

There is no soul.

Re:Are we really this smart?

[MajesticFiles]

You got me to thinking about the physical aspect of the brain as opposed to the "soul" for lack of a better word. The best example I can think of to illustrate my point is amnesia.

Some times amnesia is the result of physical damage to the brain, but it also can be the result of psychological damage that has nothing to do with the actual, physical brain. The brain can be completely undamaged, no tissue damage, no cellular damage, but the memory is gone. Now imagine a brain taken apart molocule by molocule and the re-assembled.

Will our memories survive this? It seems they aren't really a part of the actual cells and molocules and atoms that compose the physical brain...but something else. Something that even scientists can't quite put their finger on. And if we're not sure what it is that really makes us who we are, how can we transport it?

Re:Are we really this smart?

[Mandelbrute]

what of that vaporous non-matter that is so imporant? Our memories, our knowledge, all that is us?

We don't even know whether those things are vaporous or not.

In the thirteenth century, the Emperor Frederick conducted a gruesome experiment where he sealed a man in a jar with a thin (but airtight) paper seal, to see if the escaping spirit or soul would break the seal. Theological thought at the time was that the soul was invisable, but made of solid matter.

We are still not capable of artificially creating thoughts because we still cannot define them. We will get a few more clues if we can copy someone and see whether they retain their current train of thought.

-----------------

An insubstantial man is vaporwere.

Re:Are we really this smart?

[Anonymous Coward]

Believe it or not, our memories and knowledge are not stored via black-magic in an unknown mystical misty substance in our heads, but by good old solid molecules etc that physically make up our brains. An exact replica would have ALL of that, just like an exact replica of a hard disk would have all of that hard disks information. Believe it or not, human memory is not a mystical force that defies physics, our brains are subject to precisely the same physics laws as every other part of our body. Nope, no defying-of-physics going on inside our heads. Its good old plain old real matter in there, and its certainly not "vaporous" (with the exception of the presence of some gasses, which are of course, once again, just good old molecules, plain old matter, the same electrons/protons/neutrons that our "skin and bones and blood" are made up of).
Dude, take some chemistry courses and physics courses. Our brains are not mystical metaphysical things. The existence of sentience (related to "consciousness") eludes explanation of course, and thats where it might get a little dicy, but memories and knowledge and thinking and reasoning are things that are, unfortunately, made up of matter and have not been granted exemption to the laws of physics.

Re:Are we really this smart?

[Anonymous Coward]

All of which is why, of course, the brain is still so subject to modification and damage, e.g. a little bit of brain damage can seriously affect all of memory, knowledge, thinking and reasoning. Which "proves" in at least some way that the memory and thinking and reasoning was the result of the *physical* configuration of the particles in the brain, not something vaporous or non-matter. It also explains why not only thinking and reasoning, but CONSCIOUSNESS itself (might be called a "soul" by some) is so horribly easy to influence even with a few simple drugs. If our "souls" are so absolute, then why would it be even possible for a small amount of a single specific chemical (i.e. alcohol and drugs) to have such drastic influences on the way we *experience* consciousness? Consciousness itself must surely be a simple product of chemistry if it is so easily modified by chemicals. Same applies to emotions; if emotions are as mystical as many religous people portray, how can chemicals so easily directly modify emotion?

And things like MRI scans *reveal* a "concrete", physical structure to thought and reasoning. Chemistry analysis reveals concrete chemical causality of emotions.

Only the unified holistic *experience* of all of these things combined, which is our "consciousness", defies explanation by existing scientific knowledge, otherwise, if we can "feel", its arguable that a computer would be able to also. Where do "I" stop and my "body" begins? Where do "I" stop and the world begin? Bodies can be extended by prosthetics, even nerve endings extended by artifical "nerves", there is no reason to suspect the brain will not be "extendible" in future by more advanced electronics. Would such electronics become an integral part of an individuals consciousness?

Anyway, just some random thoughts related to the question ..

Re:Are we really this smart?

[aozilla]

Judging from your post, I'll assume that you believe memories, knowledge, and "soul" don't result merely from complex physical processes.

Define physical. A soul has the ability to act on physical objects. This is evidenced by my typing this. A soul is acted upon by physical objects. This is evidenced by my replying to your writeup. If something can be acted upon by physical objects, and acts upon physical object, what about it is different from a physical object itself?

Is an electron physical? Why? No one has ever seen one. Sure, it can be observed indirectly, but so can a soul. Sure, it follows a predictable probability pattern, but so does a soul. You could define a soul as that which cannot be descibed by any mathematical formula, but then you're including just about every elementary particle, since they all exhibit random behavior at some planck's scale.

Re:Are we really this smart?

[dragons_flight]

Amnesia is a confounding factor because before you can't deal with the loss of memory, you ought to have a good understanding of the process of memory itself.

There are theories about how memory operates, and decent experimental evidence to make a beggining at understanding it. Roughly the expectation is that memory relates to the stregthening or weakening bonds between nuerons, and the tendancy for nerve clusters to repeat firing patterns that have occured previously. If memory can be explained physically then it would probably suggest an answer to psychological amnesia as well.

Many mental illnesses (depression, schizophrenia, OCD, etc.) exhibit detectable physical anomalies in the brain, even in the absence of trauma. Of course causality is hard to establish, but it does support the idea that mental changes might always have accompanying physical changes.

If you are interested in Mind-Body connections, Brainstorms by D. Dennett is excellent. Also, Philosophy of Mind by Georges Rey is not quite so interesting to read but particularly thorough. Rey devotes the last several chapters to the detailing one of the more respected modern theories concerning the principles of human cognition and thought, and how it might come to arrise from a highly ordered but purely physical system.

Re:Are we really this smart?

[koreth]

If memories and knowledge exist outside the body, why do people suffer memory loss and personality shifts after severe brain injuries?

If it's because the soul is connected to the body in some way, who's to say the connection has anything to do with physical location? Your vaporous, non-matter soul might transcend time and space, and the fact that its shell is suddenly over there instead of over here might make no difference.

For that matter, who's to say it couldn't attach itself to both copies of you, or even split into two copies of itself, if you were duplicated? Since it's undefinable and immeasurable, any assertions about what it can and can't do are unfounded. To my knowledge no religious texts address the issue of teleportation. Unless you count Star Trek as a religion. :)

Original article from Phys. Rev. A...

[frank_adrian314159]

... is here. Sadly, just as you need a subscription to read the Nature article, you need a membership here, as well (or be willing to pay $15.00 via CC for an immediate download). You can't even get a preprint or tech report at Aarhus. Is it just me or are others starting to feel as if technical information, which was once disseminated for little or no cost, is now becoming increasingly expensive?

Oh well, welcome to the "Age of Access"...

please god no more Star Trek references

[akondo]

the reason we "laugh" at Star Trek is because it does such a dippy, ignorant, bad job of recycling the world's sf ideas, dressed up in a sappy soap opera shell and performed by the worst actors the galaxy could muster. The idea of a teleporter was not originated on the damned program. Not that this is a teleporter anyway, at best it might someday offer some sort of "simultaneous" communications - like the Ansible from Le Guinn's The Dispossed.

Every time a remotely sf idea get mentioned on it some bloody fool comes along and blabs about the uncanny similarity to Star Trek..

SHUT UP! SHUT UP! SHUT UP! YOU ARE BORING EVERYBODY!

Destroy the Sun!

[Anonymous Coward]

"Since the beginning of time, man has yearned to destroy the sun"
-- J. Montgomery Burns

Ignoring the fact that this technology does not permit the transmission of matter, only information ...

If one could teleport matter, how much cadmium or other neutron absorber would one have to teleport into the sun in order to quench the nuclear reaction and make Burns' dream a reality? Or would it just not work at all?

Re:Destroy the Sun!

[TheSHAD0W]

Quench the sun? Not likely. The sun could swallow the entire Earth, much less its Cadmium content, with only mild indigestion (astronomically speaking). You'd need a lot more than that to actually put it out.

Re:Destroy the Sun!

[datarat]

Actually, troops, the scary news is that there is evidence that the nuclear reactions at the sun's core HAVE gone out. Nothing conclusive yet, but we may have already missed the boat.

...but...

[J.J.]

...but was published in Nature 27 Sep 01.

As far as I'm concerned, I'd rather hear about it now, instead of back in June. Then it was just a paper presented at a conference. There's thousands of those, and I've presented a few myself.

Now, however, it's a paper that's been published in Nature. Can't say that I've ever had that distinction.

J.J.

+1 Funny on the MQR standard

[MarkusQ]

• Nature is a peer reviewed journal, and one of the more prestigious ones to boot.

-- dragons_flight

Damn, here I've been going under the misapprehension that nature is a big open place full of green things and other things that can poop on you. -- ENOENT

Sheesh! Do mod points destroy your sense of humour? This was clearly a joke! I can't give you karma, but I can give you my appreciation, which trades for karma about 3::4 on the junk bond market.

-- MarkusQ

quantum communication == private communication

[Anonymous Coward]

Teleportation may be years away, but there are much more important implications for privacy of communication. Using the same principle, one could teleport a message to a pre-set destination and be sure that it would arrive unintercepted.

This is not conventional copying

[gotan]

You can not duplicate a quantum state. You can create two electrons with identical spin, but what you can not do is, taking one electron with an arbitrary spin and prepare a second electron with identical spin without altering the first one. What you can do is 'transmit' the spin from the first to the second electron. But in the process the spin of the first electron will be destroyed. To do this you need quantum entanglement between the affected electrons, maybe mediated by something (polarized photons maybe) and maybe a transmission of conventional information (the result of a mesurement process).

A spin is only an example for a very simple quantum object, a more complex object is just described by more quantum states (this is of course a huge understatement, working with more than simple assemblies of a few spins poses a lot of technical problems, and that is where the experiment made a major contribution). You can 'classically' copy an object (that is, you can put all the right atoms at the right places) but you can not copy the quantum state, you can only transfer the quantum state from the first object to the second (and maybe even transfer state 2 to object 1 in the same process), so the question is, if a 'classical' copy is sufficient to 'copy' a person, or if the quantum state makes all the difference.

Re:This is not conventional copying

[Thing 1]

so the question is, if a 'classical' copy is sufficient to 'copy' a person, or if the quantum state makes all the difference.

To venture into the spiritual (not religious!), perhaps the quantum state of a human is the equivalent of the soul.

Teleporting a car, or a computer, or office furniture should be okay, since those do not operate or depend on the quantum level. However, "teleporting" a human without the quantum state would result in a perfectly duplicate, yet inert corpse.

I like your idea -- create the "corpse" at the destination, then swap the quantum states of the human and the corpse, and *poof* teleportation! (I won't be the first though... Thing1Fly...)

I've been doing a lot of thinking about the relationship the quantum world has to things spiritual for several years. It started in April of 1999, when I read an article which stated that the human brain works on quantum principles, in addition to chemical, mechanical, and biological. So if we want to create a computer as powerful as the human brain, we'll have to understand quantum mechanics.

Three weeks later, I read an article which stated that we've identified one quantum principle, and demonstrated it in the lab: entanglement. This is Einstein's "spooky action at a distance." Through a process, two electrons become entangled and when separated (by up to 10 km so far, at the time), changing the spin of one would immediately change the spin of the other.

This proved to me that telepathy is possible. And then I considered the anecdotal evidence: you hear all the time about a mother knowing when her child's in danger. Yet I have not once heard that a father knew. Given that evolution tends to take advantage of phenomena, our brains are using this quantum effect to provide better protection for our children. The genes that program for this, are more fit for survival. We must be just starting out in exploring this genetic path, because it's not very controllable, and YMWV greatly.

The child spends 9 months in the womb. 9 months in which the mother and child can spend becoming entangled. I think that's really cool, and raises a neat question -- did wombs evolve in order to get the quantum effects? After all, it's a lot easier to flee from a predator and leave your eggs behind than it is to lug them along with you -- so there had to be a compelling reason for females to give up their flight ability.

Re: This is not conventional copying

[Inthewire]

Very much inline with my thoughts on the subject.
How very...nah.
Thanks for the link, too...I think I'll reread this a few times and think about it often.

Don't Lie

[Anonymous Coward]

Don't lie, I saw you laughing over dinner.

Darn it

[Anonymous Coward]

Ruin my fun...

So will Quantum Entanglement be the ultimate net?

[narfbot]

Think about communicating as the speed of light, with no wires. There would be no barriers to net communication and speed.

But terrorists trasmitting their plans over the internet will likely be unstoppable, ..
...unless we could make some kind of Quantum Entanglement Feedback, and blow up their computers and themselves.

The Outer Limits [OT]

[Anonymous Coward]

It was a relatively decent show, yes, but the way they ended it was really stupid. That bit at the end of every episode where they had some guy with a deep voice saying something trite that we're all supposed to think sounds really profound, or that it conveyed some really deep moral or something. Half the time it was just cliched tripe. That was corny, they should have just done away with that ending bit, and the show would have been better for me.

Ultimate Key Exchange

[jon_eaves]

It may not be teleportation, but it's certainly
the ultimate key exchange. Here let me generate
a secret key at my end. Now, with my QE I twizzle
the magic at this end. Bingo ! Instantly reproduceable at the other.

Better not let the terrorists get hold of this.

Cheers,
-- jon

Xarchives Mirror of the paper [maths here]

[-douggy]

There is a mirror of the paper here at the arXiv.org e-Print archive. 11 pages of pdf fun can be found:

HERE

Have fun!

"told you so"

[Nihilanth]

I find it gratifying that an earlier comment of mine about quantum entanglement was rudely put down as "impossible outside of science fiction and dilbert cartoons" is now receiving some front-page lovin'

Moderation

[BadBlood]

OK, how the hell do you moderate some of these comments? Not only do you need a phd to comment, but you need one to judge the merits of said comments.

Christ, I thought reading the article itself was hard enough....

Re:Moderation

[Anonymous Coward]

hehe, its true

Reality of it

[Efexis]

Some people seem a lil confused here about the teleportation aspects of this, but the reality of it is that quantum entanglement doesn't allow the teleportation of an object to any arbitrary location... you have to first split your particles (to create the entangled state), then move one of them to another location. Changes made to one of them would have the oposite effect upon the other. The theory is along the lines of, if you use one of these particles to "observe" another particle (eg, firing them at each other), the energy changes would be mirrored by the other. As we all know, observing something destroys (or at least, changes) it. As the oposite effect happens at the other side, this could be used in combination with another paticle to recreate what you just destroyed. So you could only transfer your object to whereever you've put your reciever.

However you do run into problems... firstly, if you don't reacreate the whole object fast enough, you get problems... as you're moving parts of atoms at a time, and atoms don't really like existing half here and half there, and will tend to break up and shoot off in all directions.
Secondly, you can't read data smaller than the reader... should a particle be undergoing a quantum event (eg, quantum leap while changing frequencies), you'll lose that data.

Quantum entanglement is really not all that strange... it's just particles that exist in different locations in space at the same time, as opposed to most of what we interact with, which are particles that exist in one location in space, but many locations in time. What I'm keen to see is if anyone can create a particle in more than 2 spaces... that opens the window to transmitions being monitored... and if "teleportation" is ever sorted out... would mean duplication of complex atomic structures...

...food for thought

Heisenberg's principle and measurements

[sigwinch]

Entanglement and Measurement (as defined in Quantum) are mutually exclusive propositions.

I suspect, though, that it can be proven that a minimum amount of energy must be used to entangle a pair of particles, analogous to Heisenberg's principle. Figure out whatever that energy amount is and multiply by the number of particles in the object. For the human body, the number of particles is on the order of 10^26. Let's be generous and assume that the amount of energy is a mere 0.1eV per particle. Multiplying 10^26 by 0.1eV, and using the conversion factor of 1.6*10^-19eV/J, we get 1.6megajoules. 1.6MJ is a considerable amount of energy, equal to the kinetic energy of 300 .50-caliber rifle bullets, or enough energy to run a toaster for 20 minutes. If the energy is evenly applied, you're toast. If it's uneven, you're gravy. Regardless, you are no longer among the living.

Even if you reduce the energy by many orders of magnitude, it is still a lot. Thus I don't think large-scale teleportation will ever be practical without tremendous advances in basic physics. However there are intriguing possibilities. An ensemble of a trillion or so particles may be small, but it's not worthless. E.g., you could deposit a small array of nanodots using atomic-force microscope lithography (at great cost), then replicate them across an entire wafer using teleportation. Or you could use it to grow a nanowire along a chosen axis: the coherence length would only need to be tens of Angstroms, and the coherence time would only need to be nanoseconds. Teleportation lithography would be low temperature, which would vastly expand the materials available to the designer (conventional semiconductor lithography materials have to survive temperatures of 500 deg. C or worse, which rules out all sorts of otherwise useful substances).

transporters and terrorism

[Anonymous Coward]

the one good thing about teleporting people as a means of transportation is that there would be less planes to hijack and smash into buildings. i mean you could smash a person into a building, but i'm not sure that it would have the same effect, people not being composed of mass quantities of jet fuel and all. the only problem is that maybe you could just teleport a bunch of jet fuel at the building. hmmm. maybe a good anti-smoking add. hehe.

Bandwidth vs Latency

[gregm]

No it's bandwidth here....

Their method is still limited to the speed of light... They're using a laser to "connect" the two hunks of matter. However they're saying they can transfer the state of trilions of hunks of matter at near light speed. That's serious bandwidth with some darn fine decent latency.

G

Beaming == Copying

[anshil]

One thing enterprise completly misses, is that once you can do "beaming" you can also as good -copy- any mass including you.

This different as cloning, since your duplicate would really have absolute the same structure, including same memory and same beeing. Only the ultimate old question is left if there is something like a soul :o) and if if it gets copied too.

"Beaming" would function in reality like sending a fax, not like the original enterprise serier used it to save production costs (No lander spec. effects required). Yes the other side receives the image, but the original is still there. I personally do not want to be beamed that way.

First teleportation experiment

[Anonymous Coward]

...In 1998 what has been described as the first teleportation experiment was done when scientists at the California Institute of Technology teleported a beam of light across a laboratory bench...

"Ready ... Set ... <Click> Can you see it? Can you?"

Speed of light

[Placido]

Talking about wierd things happening at the speed of light - the wierdest thing I've heard about is that if you're travelling near the speed of light and you shine a light in the direction of travel, the light would travel away from you at THE SPEED OF LIGHT! Thus the light beam is travelling at almost twice the speed of light! Can anyone confirm this?

Arrrghhh! My head!

Re:Speed of light

[Anonymous Coward]

Exactly, the fundament of relativity: speed of light is always constant. No matter at what speed you move. So everybody sees it as the speed of light, and not as you imply twice the speed of light.

But how can one avoid Supercooling?

[mrthoughtful]

Given that one -could- teleport animate matter (e.g. Spock) using some technology derived from quantum entangling, surely it is imperative that the matter to be teleported be kept at near-zero kelvin, otherwise you are talking about a load of mush at the other end. I love the idea of telling nearly every particle to "Keep still while we transport you!"

lets talk ...

[Anonymous Coward]

I think before we teleport stuff a BIG use would be communications. Imagine 0.0ms ping time to any computer on the planet.

And the winning of Best Overstatement is ...

[Greedo]

regarding teleportation. it's simple.

I'm sorry, but that's got to make you laugh.

You may be wrong

[Illserve]

Yes, initially the particles have to travel at the speed of light to reach the destination, but once there, the travel of the collapse is instantaneous.

So let's so you have 2 communication stations, each has 1 billion particles in storage, tied to one another and sequentially numbered. By collapsing the wave of a particle on one end, they can send one bit of information to the other instantly. Again, the only drawback is that you have to initially send the particles at light speed.

Re:You may be wrong

[krlynch]

each has 1 billion particles in storage, tied to one another and sequentially numbered

Ahh, but you can't do that! The "wierdness" of QM (it isn't really that wierd, just different than what you are used to) includes the "indistinguishability" of identical particles: you can't attach a number to particles that you aren't observing. If you know where a particle is, you have already collapsed the wavefunction and disentangled it. If you don't know where it is in a collection of identical particles (so that you don't collapse the wavefunction before you apply your "information transmission algorithm"), then you don't know which label you gave it originally. When the wave function is "collapsed" at the remote station (which has the same identification problem you do, by the way, so they can't actually do this, but let's ignore that for now...), and one of the particles "collapses" at your station, you, even if you could figure out that the "collapse" has occurred, have no idea which bit of information you are looking at! All you would know is that one bit was transmitted, but that doesn't give you any information whatever. Of course, there are many other issues with you algorithm that make it worthless for information transmission, and I only focused on one of the problems. Quantum mechanics is VERY DIFFERENT from classical mechanics, and most analogies from the macroscopic world are absolutely incompatible with the way reality actually seems to work.

Not as big a jump as it sounds

[mmacdona86]

To do anything like teleportation, you would need to entangle all the quantum states of all the atoms. Here they entangled 1 quantum state that was averaged over all the atoms. This is quite a bit easier; some may even call it cheating. It means that even though you have "macroscopic" entanglement, you don't have "more" entanglement than if you had simply entangled two individual particles. It is an interesting experiment nevertheless, since it shows how some degree of entanglement can be achieved over populations of particles. Even though no pair of cesium atoms in the two samples was entangled on its own, the population was entangled when you averaged their states. As far as "practical" uses of entanglement (encryption, computation) this is an incremental advance at best.

Explanations of entanglement and teleportation

[hubie]

Here are two pages that explain very well quantum entanglement and quantum teleportation:

Quantum entanglement

Teleportation

prove it by creating a quantum radio

[Anonymous Coward]

all they have to do is put a machine on the moon and a machine on earth, and use the quantum machine to send a YES/NO bit to the other end, and if its faster than light speed, then I will be impressed. until then... humbug!

Preprint availible at LANL

[kgp]

You can find the preprint at

http://xxx.lanl.gov/abs/quant-ph/0106057