Quantum teleportation achieved over 16 km

May 20, 2010 by Lin Edwards report
a, A birds-eye view of the 16-km free-space quantum teleportation experiment. Charlie sends photon 1 to Alice for BSM. Classical information, including the results of the BSM and the signal for time synchronization, is sent through the free-space channel with photon 2, to Bob, before decoding and triggering of the corresponding unitary transformation. b, Sketch of the experimental system. See the original paper for more details. Image copyright: Nature Photonics, doi:10.1038/nphoton.2010.87

(PhysOrg.com) -- Scientists in China have succeeded in teleporting information between photons further than ever before. They transported quantum information over a free space distance of 16 km (10 miles), much further than the few hundred meters previously achieved, which brings us closer to transmitting information over long distances without the need for a traditional signal.

Quantum teleportation is not the same as the teleportation most of us know from science fiction, where an object (or person) in one place is “beamed up” to another place where a perfect copy is replicated. In quantum teleportation two photons or ions (for example) are entangled in such a way that when the of one is changed the state of the other also changes, as if the two were still connected. This enables to be teleported if one of the photons/ions is sent some distance away.

In previous experiments the photons were confined to fiber channels a few hundred meters long to ensure their state remained unchanged, but in the new experiments pairs of photons were entangled and then the higher-energy of the pair was sent through a channel 16 km long. The researchers, from the University of Science and Technology of China and Tsinghua University in Beijing, found that even at this distance the photon at the receiving end still responded to changes in state of the photon remaining behind. The average fidelity of the teleportation achieved was 89 percent.

The distance of 16 km is greater than the effective aerosphere thickness of 5-10 km, so the group's success could pave the way for experiments between a ground station and a satellite, or two ground stations with a satellite acting as a relay. This means quantum communication applications could be possible on a global scale in the near future.

The public free space channel was at ground level and spanned the 16 km distance between Badaling in Beijing (the teleportation site) and the receiver site at Huailai in Hebei province. Entangled photon pairs were generated at the teleportation site using a semiconductor, a blue laser beam, and a crystal of beta-barium borate (BBO). The pairs of photons were entangled in the spatial modes of photon 1 and polarization modes of photon 2. The research team designed two types of telescopes to serve as optical transmitting and receiving antennas.

The experiments confirm the feasibility of space-based , and represent a giant leap forward in the development of applications.

The paper is available in full online at Nature Photonics.

Explore further: 'Smart' bandage emits phosphorescent glow for healing below

More information: Xian-Min Jin, Experimental free-space quantum teleportation, Nature Photonics, Published online: 16 May 2010. doi:10.1038/nphoton.2010.87

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Bob_Kob
2.3 / 5 (4) May 20, 2010
Im confused, what is a free space channel? How long did it take the information to transmit and what does it have to do with teleportation?
mlange
3 / 5 (3) May 20, 2010
Im confused, what is a free space channel? How long did it take the information to transmit and what does it have to do with teleportation?


free space channel is where light freely propagates through the atmosphere. Fancy word for empty space.

I'm not sure if they've measured entanglement successfully. anyone? i'd love to know. but the information exchange is way faster than light.

Teleportation is kinda for the headline. They are teleporting information; by this i mean when two photons are entangled, regardless of their distance apart, when you "view" one photon, you can with almost certainty guess the "change" in the entangled photon miles away. Hence, information transfer at much faster than light.

Raygunner
3.5 / 5 (8) May 20, 2010
By much faster than light you mean instantly, right? To date, there has been no "change" delay measured between entangled photons that I know of. 30 years from now Verizon and ATT will supply an EP-Card (entangled particle card) for your cell phone. It will have the match back in the Central Office. All incoming or outgoing info (data, calls, whatever) will be INSTANTANEOUS and, even better, will NOT USE RF OR FREQUENCIES for the link. Imagine that - no such thing as "bandwidth" or "frequencies" anymore. Eventually everything that links will have an EP-Card, even television - no more RF! Heck, we could have them implanted and wired in and have entangled-thought transfers (maybe your vision too) instantly - whether on Mars or across the room. With mass production, the earth would truly become silent - RF wise and even with communication. If you send/receive in your brain - why even talk or turn on the TV? The Govt will LOVE this! Just rattling off here.
Noumenon
4.5 / 5 (64) May 20, 2010
I thought it was already proven that Quantum Entanglement can NOT be used for faster than light communications.
NeuroPulse
not rated yet May 20, 2010
Im confused, what is a free space channel? How long did it take the information to transmit and what does it have to do with teleportation?


Free space, as opposed to inside something such as a fiber optic cable.

Teleporting information instantly form one location to another without traveling the space in between.
Noumenon
4.5 / 5 (52) May 20, 2010
Observation of wavefunction collapse can lead to the impression that measurements performed on one system instantaneously influence other systems entangled with the measured system, even when far apart. Yet another interpretation of this phenomenon is that quantum entanglement does not necessarily enable the transmission of classical information faster than the speed of light because a classical information channel is required to complete the process. -Wikipedia


One would still have to convey some info about the measurement, so it can't be used as a practical technology.
Skeptic_Heretic
4.1 / 5 (7) May 20, 2010
I thought it was already proven that Quantum Entanglement can NOT be used for faster than light communications.

There's a question of whether that is the case. The reason being that once you view a particle you break entanglement. So your communication would be a single bit per entangled particle with no manner of recycling. Sort of like cell phone minutes. Plus in order to ensure you've received a decodable message you need some sort of established system by which you verify the communication, which unless also entangled must travel at a known speed, ie: light/emf.

I don't think it's impossible, but it is certainly beyond our current understanding as to how one would enable quantum communication.
Noumenon
4.5 / 5 (55) May 20, 2010
It only appears that communication through entanglement is FTL when rationalized within the context of a classical conceptual framework. Nothing actually travels from point A to point B FTL, so therefore it cannot used as though such was the case,... or as if the observers classical interpretation, (given inherent subjective intuitions of time, space, causality) was not a component of the phenomenon.
SteveL
4 / 5 (1) May 20, 2010
There will always be bandwidth and frequency limitations. The electronics that drives the communication equipment will always be limited on how fast it can convert and move data to the transmitting device and the same limitations will exist on the receiving end.

When the PC first came out with a 10 meg hdd, it was supposed to be more than we would ever need. When the internet came out with IP addresses, there were more than we would ever need. Nature abhores a vacuum and will always fill it. It doesn't matter how much bandwidth or capacity is available - eventually it will be insufficient.

Multiplexed entangled channels might be the best way to run parity bits, packet and data checking.
KronosDeret
3 / 5 (2) May 20, 2010
Well Ill be damned, i thought you cant transfer any usefull information, you can just compare measurements from two distant points. How to encode and decode information would be then completely different subject.

It is ofcourse possible that its not so and we will be shown a communication pair capable of instant digital comunication without any radio, optical a electrical signal.

Im optimistic, i think it is possible. Only the time will tell.
CSharpner
4.8 / 5 (4) May 20, 2010
Im confused, How long did it take the information to transmit and what does it have to do with teleportation?


How long: Time is not a factor when two particles are entangled. There 2 points in time that count: When the entanglement began and when it ended (the measurement). The "transmission" from particle A to B is a result of some measurement on A. It's somewhat misleading to say the measurement on A "then" causes a result on B. A's manipulation causes A's and B's state, but A's cause can come AFTER B's measurement. Both particles have that state (if it could be said they have state without being measured) throughout the entanglement time period. In the quantum world, effect can proceed cause.

Classic info: No classic info is known about A when a quantum measurement is done on B. One must /wait/ for a classic (slower than light speed) transmission from point A to point B to do a comparison.
CSharpner
1 / 5 (1) May 20, 2010
and what does it have to do with teleportation?


Teleportation is the act of transmitting quantum information from one particle to another. It's not "Beam me up, Scotty". Entangle two particles and manipulate one and the other responds (not necessarily in that order (see my post above). That's all teleportation is.
dtxx
1 / 5 (3) May 20, 2010
Why does error correction have to be on a separate channel? I don't see why it would.
Skeptic_Heretic
not rated yet May 20, 2010
Why does error correction have to be on a separate channel? I don't see why it would.

Because you would require an infinite amount of channels to correc for the error on the error correction channel and another channel to correct for that, and another to correct for that.....
VultureTX
4 / 5 (1) May 20, 2010
You need an outside conventional channel to to tell you to measure the other half of an entangled pair.
Because entanglement is bi-directional measuring either photon breaks entanglement and voids any info transfer from the other side.

Now once we get a massive qty of entangled pairs and can sequentially access them, a outside channel could be used to start a measured reading of photons in order thus creating a data stream. Except as of now you can't control the data because it is whatever the "measurement" of that entangled photon is. Sorry no FTL link for you, but thanks for informing us about your photons.
nuge
4.7 / 5 (6) May 20, 2010
No no no no no no no NO. this article is misleading and a lot of the comments are all wrong. No. The actual information itself must be sent at subluminal velocity. The superluminal entanglement part is only half the story. Make no mistake, quantum stuff is spooky but it isn't magic.
Skeptic_Heretic
3.7 / 5 (3) May 20, 2010
The actual information itself must be sent at subluminal velocity.

Computers function by measuring 1's and 0's. Entaglement can be measured by spin, up or down.

Information can be carried through quantum means, the problem is in reading and coordinating that information. You're incorrect in your assertion.
Bob_Kob
2 / 5 (4) May 20, 2010
Ok followup question, if quantum entangled particles instantly change regardless of distance, this means that there is no intermediate em wave sent?

So lets say 2 parties have entangled phones, it would be impossible to intercept the transmission in any way?
Noumenon
4.5 / 5 (53) May 20, 2010
Correct, there is nothing in between them (no hidden or unknown variables). The two phones would be described as one single device until the wavefunction collapsed due to a measurement/ decoherance. However you still cannot send unknown info to the receiver because a classical correlation has to occur.
dtxx
2 / 5 (3) May 20, 2010
So in the instance of the two phones, you aren't sending information faster than light, because regardless of how quickly decoherence occurs you still had to send an entangled photon from alice to bob.
Skeptic_Heretic
3.7 / 5 (3) May 20, 2010
So in the instance of the two phones, you aren't sending information faster than light, because regardless of how quickly decoherence occurs you still had to send an entangled photon from alice to bob.
No, Alice and Bob's entangled photons would have to have been entangled before either attempted to use them. There's no send.

If you both went to the Verizon store and both bought a phone which could only call the other phone, then you'd have a more apt analogy.

Let's say you and I can use QE to talk on a phone.

Now you want to call your mom. You can't use that phone. You'd have to have another QE phone that was used specifically to call your mom.

Again, right now we do not have a strong enough understanding of entanglement to say we can or can't use it for communication. At our current understanding the answer is No we can't, however, much like flying, we eventually figured it out.
drel
5 / 5 (7) May 20, 2010
Here is how i understand it using grade school terms.

I have a printer that spits out random letters. You have a printer that does the same. BUT the printers are correlated so they both print out the same letters. the letters ARE random. No one knows what letter will be printed next, but the 10th letter printed on both printers will always be that same.

you can take the list that YOUR printer prints out and use it as a cipher to encrypt a message that you send to me. Since said cipher is always 100% random there is no way to "crack the code" unless you have the other printer (or the original printout)
so you sent you encrypted message to me. I can at anytime (even before you encoded the message) turn on my printer to generate a cipher on my end to use to read your message.
drel
5 / 5 (5) May 20, 2010

The next letter to be printed can always be any letter. the next letter is said to be in a supposition of all the states (letters), but once I have printed out a letter on my machine your machine WILL print out the same letter. That is the "SPOOKY ACTION AT A DISTANCE"

The above info is not 100% scientifically correct but I believe it explains it at a more basic level
paulsac
2 / 5 (3) May 20, 2010
communication between multiple devices would be perfectly possible and nearly instantaneous assuming only that we can have a way to keep individual entangled particles separate from each other (to keep their quantum state) and yet close enough to be controlled by a processor reasonably.

Entangled particles would be "read" at a central location, and transferred to encoded destination.

Limiting factors are due to (for now) binary electron-based processors. (encoder, transfer, receiver)
Skeptic_Heretic
1.3 / 5 (3) May 20, 2010
communication between multiple devices would be perfectly possible and nearly instantaneous assuming only that we can have a way to keep individual entangled particles separate from each other (to keep their quantum state) and yet close enough to be controlled by a processor reasonably.

And how does that processor communicate? If you said "through quantum entanglement", slap yourself. This is why people say that currently, QE cannot be used for communication. We don't have a controller capable of controlling the observation over distance without using non QE correlation.
Entangled particles would be "read" at a central location, and transferred to encoded destination.

As soon as you "read", the entanglement will cease to be.
Spacetime2020
3 / 5 (4) May 20, 2010
There is no instantaneous information transmission in quantum teleportation. If that was possible, travelling people would disagree about the time-ordering of the events: while it would be seen as instantaneous by observers at rest relative to the transmitter and the receptor, observers travelling towards the receptor would say that the reception ocurred before the transmission, thus violating causality. What happens, according to the Manyworlds Interpretation (which is not widelly accepted) is just that sender and receptor agree that they are in the same branched universe.
Skeptic_Heretic
5 / 5 (3) May 20, 2010
There's no reception or transmission within QE.
Blicker
1.7 / 5 (3) May 20, 2010
What is confusing is the experiment only sends a photon through space because presumably no current technology to trap and store photons.
This is what I think is intended.
A photons trap 'lightbox' is needed to hold vast numbers of photons in an ordered manner numbered 0 to N.
Any one trap acts as transmitter/receiver.
A 'charger' machine generates entangled photons and spews them to alternate traps; one photon into the transmitter trap; its entangled 'twin' in the receiver. The next pair likewise etc.
A takes his trap to Mars. He might be over 20 light minutes away.
Mission Control (MC) keep the twin trap on Earth.
MC's message in binary digits 'sets' photons in sequence to 1 or 0. This INSTANTLY sets their twin photons to the same on Mars.
At his leisure or in real time, A's trap on Mars reads the photons to provide the message.
The machine keeps track of which photon it has reached. The 'used' photons cannot be used again.
Caliban
1 / 5 (5) May 20, 2010
They state pretty clearly in the article that they are making- or so I read it- multiple changes in state for a single pair of entangled photons.

If this is so, then apparently the entanglement doesn't collapse or decohere or whatever, and so transferring information is indeed possible.

Assuming this is the case, the immediate application would be for two devices that are ENORMOUS distances apart, as spacecraft and exploratory satellites are from Earth, as this would mean no time elapsed in sending/receiving, as opposed to normal delay in ordinary EM transmission due to the speed-of-light maximum inherent in EM propagation.
CSharpner
5 / 5 (1) May 20, 2010
Blicker, everything you said is true and could/would/will happen, but you're leaving out one CRITICAL piece to all this that newcomers often do: You still need a "coincedence counter"... something to send from A to B sub-luminally so that you know the timing of the readings. You can't read any useful information without that. Without the CC, all you'd see would be garbage. Correlation information can't be known at the receiving end until classical, slower than light, information is transmitted about the quantum measurement. That's the catch.
CSharpner
3.7 / 5 (3) May 20, 2010
Caliban, I read the article again. The article did not state they made multiple readings of the same photon pair. And, if the article did say that, it would be an author error. In QED, it's well know that you can't do that. If they ever break that, it'd be HUGE news.

Additionally, even if they could read multiple times without breaking entanglement, there's no reason at all that that would suddenly enable them to transmit classical information without a sub-luminal coincidence counter.

In short, you can't transmit classical information faster than light, instantaneously, or backwards in time... at least, not with this technique... not with the way the wishful "newbs" here are wishing. :)

Also, a note to everyone else trying to find ways to use this to transmit classical info FTL: Stop using the phrase "instantaneously" as that has no meaning here, especially when point A and point B are in different inertial frames. Basic relativity folks... "Instantaneous" has no universal meaning.
Ed_from_NY
2.7 / 5 (7) May 20, 2010
I conduct the follow "experiment" I agree to write the letter A and the letter B and place each randomly in one of two cardboard boxes. I then send one box 10,000 miles away. At exactly 12 noon GMT the recipient opens the box and knows "instantaneously" both the letter received and the letter not sent (10,000 miles away).

This exactly like two entangled photons is a completely uninteresting result. And has no utility.
Question
2 / 5 (4) May 20, 2010
It appears Ed of NY is about the only one that understands what is going on in these entanglement experiments. Boring!
Drkwing
not rated yet May 20, 2010
this sounds a lot like an ansible to me.
Noumenon
4.5 / 5 (53) May 20, 2010
It appears Ed of NY is about the only one that understands what is going on in these entanglement experiments. Boring!


If you're not astonished by it, you must not understand it. It not as Edward suggests.

There are many experiments that show that entanglement cannot be rationalized; I would suggest reviewing the Bell State Quantun Eraser.
Question
2 / 5 (4) May 20, 2010
@Noumenon:
I read in an article published by NASA that stated that the "Bell inequalities" has never been scientifically proven. (I have unable to find the link to the article.)

Amazed, absolutely not! This stuff is pseudoscience which I thought Physorg had a policy against printing.

Noumenon
4.5 / 5 (52) May 20, 2010
@ Edward 

Your example is trivial & does not reflect the problem at all,...
"If each particle departs the scene of its "entangled creation", [...] with properties that would unambiguously determine the value of the quality to be subsequently measured, then the postulated instantaneous transmission of information across space and time would not be required to account for the result of both particles having the same value for that quality." -Wikipedia

Now if each "particle departs the location of the pair's creation in an ambiguous state (yet unobserved, as per Heisenberg's principle), [...] there exists a connection between the members of such a pair that defies both classical and relativistic concepts of space and time. In which case "all outcomes remain a possibility and only measurement itself would precipitate a distinct value.".

@ Question,

I'm sorry you missed the scientific revolution that is qm. Bell theorem has been proven regarding no hidden variables,. 
nuge
4.5 / 5 (2) May 20, 2010
The actual information itself must be sent at subluminal velocity.

Computers function by measuring 1's and 0's. Entaglement can be measured by spin, up or down.

Information can be carried through quantum means, the problem is in reading and coordinating that information. You're incorrect in your assertion.


No I'm not. The comment about the printer said it best. The Quantum part only gives you the CIPHER; sender and recipient can by quantum means share a set of particles with the same states (entanglement). The actual message you have to send by normal means, so that the other person can read it from their cipher and thereby recreate the message at their location.
Noumenon
4.5 / 5 (54) May 20, 2010
I conduct the follow "experiment" I agree to write the letter A and the letter B and place each randomly in one of two cardboard boxes. I then send one box 10,000 miles away. At exactly 12 noon GMT the recipient opens the box and knows "instantaneously" both the letter received and the letter not sent (10,000 miles away).

This exactly like two entangled photons is a completely uninteresting result. And has no utility.


I'll try to fix your broken analogy;

You place a coin in each box and send one 10,000 miles away. The box is designed so that when the lid is closed (unobserved) the coin is made to randomly bounce around inside, and each box can take on one of TWO values when observed. For two Unentangled coins you expect the probability of observing heads when the lid is opened, to be 1/2 for each, independently. This is demonstratable and of course is obvious. If however the two coins where entangled, the probability of observing heads would NOT be 1/2 for each!
Noumenon
4.5 / 5 (52) May 20, 2010
...To determine that probability, you would arrange and send dozens of entangled ordered pairs of such boxes, and each observer would record a log of outcomes. Once the logs are compared the probabilities are NOT as expected if the boxes are considered independent. See the article "Entangled Choices" at mathpages, for a good description.
holoman
1 / 5 (3) May 20, 2010
This is old news for Colossal Storage's "Entangled Atomic Particle Communication and Holographic Quantum Memory" published 8 years ago on their website.

Bob_Kob
4 / 5 (4) May 20, 2010
But wasnt the point of this not superluminal information transfers but data transmission that is not impeded by interference?
eachus
1 / 5 (4) May 21, 2010
It is amazing to see the vehement opposition to FTL communication here, when physicists bit the bullet on that a long time ago. For decades the mantra was that FTL travel is equivalent to time travel*, and we all know that is impossible. However, theorists started playing with what happens near black holes, just in time for the first black holes to be unambiguously discovered. There were years, decades actually, of ideas such as "cosmic censorship." They all came to naught, and the American Physical Society announced at their annual meeting that FTL was possible. They had in mind some version of the Alcubierre drive, but that is a detail. Once you start warping space significantly--as black holes do--general relativity requires time travel. And as mentioned above, time travel and FTL travel are equivalent.

*Shorthand for travel from the present into the past, travel from present to future is so easy we all do it. ;-)
eachus
2 / 5 (2) May 21, 2010
So what about using Einstein's "spooky action at a distance" as a practical method of FTL commnication?

You have to set the channel up by physical communication--moving entangled particles from one place to another. FTL transport, of course results in FTL communication absent entangled particles, so let's ignore that for now.

Imagine a machine that can make pairs of entangled particles with specific, known, spin. Now all I have to do is measure the spin at 90 degrees to the known spin to destroy that information in both particles. Do this with sets of say a dozen pairs, and you now have an FTL communication channel.

The physics problems come when you use photons. OTOH, producing pairs of entangled electrons with known spin in one plane is possible. Maintaining coherency over long distances is difficult, very difficult. And if you try to accelerate the electrons to near the speed of light--it is even harder to maintain coherency. But the issues are technical...
Husky
1.5 / 5 (2) May 21, 2010
Nounemon do these random bouncing coins have their own private synchronizing communication channel through space (perhaps a string as in stringtheory) or not?

If so, it must mean the two coins are really one collective coin smeared out in space/time and this is the reason that measuring heads/tails on one coin destroys the delicate channel, because you touch the whole coin, this delicate FTL channel seems only to survive as long as its shielded from classical space time.
If not, no communication channel, than it would mean that the coins were not bouncing random at all, but the coins were programmed to loop through a series of the same bounces (like two similar programmed traffic lights) at the same time, wich would make it occur to observers as if the coins/lights were actually communicating/adjusting their mutual states.
one way to determine if the private channel truly exists would be to accellerate one box with the coin, there should be no redshift in the timing of the measuremnts
Husky
1 / 5 (2) May 21, 2010
What I think makes people skeptic is that its like saying "Hey we now have this FTL telephoneline, only you can't use it for now, because once you start talking the cable breaks", this would make people think its like the invisible emperors clothes.

What needs to be done is to either make the cable more rugged or the talking less invasive to make people see the emperor really does have a t-shirt
Husky
2 / 5 (2) May 21, 2010
What I am trying to say is that it seems impossible for two seperate objects to have the same randomness, either its not random but deterministic, but we just haven't figured it out so it appears random, or its one object in a private space/time bubble as long as the bubble isn't popped by invasive measurements, now wich is it?
Gerard_Brandon
1 / 5 (2) May 21, 2010
In its most simplistic terms isn't the fact that there is a state change at both ends indicate that information has indeed been transferred?

Consider such a change to be the equivalent of a relay and that the assumptions being made about data transfer are based on data being in its current format. There is progression to be made from analog to digital to .... be confirmed.

The question should be whether you accept the experiment delivered the results based on the protocols. If it did, great. If not disprove it.
slash
not rated yet May 21, 2010
I used to think I have a halfway accurate understanding of what quantum entanglement is, but when I read the above explanations, all I understand is that it's like taking to identical copies of sealed letters to different locations, and then reading them.

I used to think postal services have been offering that kind of 'teleportation' for centuries already?

What part of my above understanding is wrong?

And what is the subluminal signal actually needed for if it doesn't matter at what time I measure the entangeld particle? Once I measure it I know that the state I measures is the same as the state measured on the other particle. So what then is additional information required for?

Mind you, this is *not* what I used to be understanding of QE; but it seems to be what the above explanations seem to imply, and it simply doesn't make sense!
Gerard_Brandon
5 / 5 (2) May 21, 2010
My reading and re-reading of the experiment suggests a sequence of events Charlie to Alice for transformation, Alice to Bob of resultant state change and Bob decodes to review state change. This indicates (or am I am missing something) that there is a synchronization that takes place before the transmission/teleportation.

There appears to be a valid encoding and decoding process at either end and not as @slash suggests that it is in fact a known result at both ends before trnasmission
Noumenon
4.5 / 5 (51) May 21, 2010
@Husky, good questions. I think your first possibility is the one to accept if you rely on current obervations, that "the two coins are really one collective coin smeared out", even though this cannot be rationalized in the 'classical' terms of spacetime and causality, so the idea of "smeared-out" is an anology.

The second possibility you mentioned, that the "coins" are preprogrammed or predetermined, is ruled out be cause of the uncertainty principal, and in that case there would have been some discoverable connection between the two, and as I mentioned above, I believe that experiments have shown (Bell inequalities) there cannot be any hidden mechanism like that if basic probability concepts are correct. Nature appears to be undeterministic at this level.
Noumenon
4.5 / 5 (51) May 21, 2010
@ Slash, your right, those explanation does not make sense because it is not representative of the problem, but even a good proper explanation "doesn't make sense", that is why qm isn't compatible with GR or classical physics.

See the wwwDOTmathpagesDOTcom reference for a decent explanation, or look up interferometer interference experiment, or the Bell State Quantum Eraser experiment, because basically these are the same phenomenon.
Noumenon
4.5 / 5 (53) May 21, 2010
,... nor should it be expected to be in accord with classical concepts, so that it "should be understandable". Why would nature go out of it's way to evolve minds with 'quantum intuitions' when the mind has clearly evolved to operate on the macroscoptic scale (not to say that Penrose idea that consciousness may operate in entangled states is wrong).

IMO, it is more rational as far as interpretations go, to replace metaphysical theories like the many-worlds interpretation, with a epistemological interpretation say based on Kant and Bohr, and then move on.
Question
1 / 5 (3) May 21, 2010
Noumenon: It appears you do not understand the experiment. It is not the same as your two coin analogy, it is like taking one coin and separating the head from the tails and tossing both halves into the air. As soon as you pick up one half you instantly know what the other half is. It is really simple. The difference, this experiment use a pulse of light instead of a coin and splits the pulse into vertical and horizontal polarized light sending them two separate ways. These two separate pulses are never both vertically and horizontally polarized, they are one or the other from the moment they were polarized, period.
Noumenon
4.5 / 5 (52) May 21, 2010
Wrong. It also works for spin measurements of particles which depend on axis chosen by the "sender". Again if you think it is merely a trivial matter you have not done your research.
Noumenon
4.5 / 5 (53) May 21, 2010
@question, I'll try to find another example I think by Bohm, where there are three possibilities.

Einstein devised the EPR experiment to in effect make a mockery of qm, to reduce Bohr's arguments to absurdity. Of course it back fired. Just based on the history, how do you account for all these great physicist to have 'missed' the 'fact' that it is simply a trivial matter and that classical physics can be used to explain it?

Btw, I was modifiy Ed's example as little as possible, but supplied references to actual experiments performed.
Objectivist
1 / 5 (3) May 21, 2010
...how do you account for all these great physicist to have 'missed' the 'fact' that it is simply a trivial matter and that classical physics can be used to explain it?

That proves absolutely nothing and is completely irrelevant. You argue much like a creationist does.
Noumenon
4.5 / 5 (51) May 21, 2010
It is really simple. The difference, this experiment use a pulse of light instead of a coin and splits the pulse into vertical and horizontal polarized light sending them two separate ways. These two separate pulses are never both vertically and horizontally polarized, they are one or the other from the moment they were polarized, period.


The orientation of the polarizations is unknown to both observers. Since they can't just magically read it off like a coin ("vert or horz") they have to agree to use one of several filters to measure a yes or no. Each guy then chooses for each pair what measurement to perform. After many such measurements the results are compared and probabilities determined, and this is where to trouble lies.
Noumenon
4.5 / 5 (53) May 21, 2010
...how do you account for all these great physicist to have 'missed' the 'fact' that it is simply a trivial matter and that classical physics can be used to explain it?

That proves absolutely nothing and is completely irrelevant. You argue much like a creationist does.


I already provided arguments and references above. If the above was my only argument you would have a point abeit a weak and irrelevent one since my statements are factually correct and quit relevent, as it has still not been determined where qm went wrong.
Noumenon
4.5 / 5 (53) May 21, 2010
Claiming entanglement to be a trivial matter is not dogmatic, when obviously no one on the planet has reconciled classical physics with qm?!? Are you a nut?
Question
1 / 5 (5) May 21, 2010
@Noumenon: Where did quantum mechanics go wrong? When it accepted the absurdity of a cat being both alive and dead in a box!

Just because you don't know something does not make it both ways any more than splitting a coin in half means the two halves are both heads and tails until someone looks at one half. It is just ridiculous nonsense. Polarization of spin, there is not difference.

Alchemistry has more merit that this quantum entanglement nonsense. At least we really can turn lead into gold.

Skeptic_Heretic
2.3 / 5 (3) May 21, 2010
@Noumenon: Where did quantum mechanics go wrong? When it accepted the absurdity of a cat being both alive and dead in a box!

Just because you don't know something does not make it both ways any more than splitting a coin in half means the two halves are both heads and tails until someone looks at one half. It is just ridiculous nonsense. Polarization of spin, there is not difference.

Alchemistry has more merit that this quantum entanglement nonsense. At least we really can turn lead into gold.

You might want to read up more on Quantum mechanics before you make such a bold statement.
Question
1 / 5 (2) May 21, 2010
Noumenon and Skeptic Heretic: Do you believe my two coin halves are both heads and tails until someone looks at one? If not why would you think the cat is both alive and dead? Or why would you think the polarization of the light or the spin is both until it is examined?

Skeptic_Heretic
5 / 5 (1) May 21, 2010
Noumenon and Skeptic Heretic: Do you believe my two coin halves are both heads and tails until someone looks at one? If not why would you think the cat is both alive and dead? Or why would you think the polarization of the light or the spin is both until it is examined?


Three words.

Heisenberg Uncertainty Principle.

Apply that to the seemingly non-causl actions we're observing within QM and it makes far more sense and establishes why conventional physics are incongruent to observation.

Above and beyond that your frame of reference is ignoring alternate frames of reference. As soon as you pass the atomic scale, direct observation alters outcome. IE: the dual slit experiment is broken when the photons are measured from beginning to end while when unmeasured the location is absent allowing for multipe viewings of the same photon in different locations without a speed determinant. Quantum physics 101.
Ant
not rated yet May 21, 2010
The fact that the article says they are using optical equipment for transmission and receiving indicates that this is line of sight. It would have to be for entanglement of long distances to work. The total distance possible would be limited to the optically possible distance. I bet they cant get it to work with a bend in the route.
Question
1 / 5 (2) May 21, 2010
Skeptic, granted the Heisenberg Uncertainty Principle places limits on observations in the micro world. But that is by no means proof something is in both states until it is examined anymore than my two coin halves are both heads and tails until someone picks one up and looks at it.
Noumenon
4.5 / 5 (54) May 21, 2010
@Noumenon: Where did quantum mechanics go wrong? When it accepted the absurdity of a cat being both alive and dead in a box!

Just because you don't know something does not make it both ways any more than splitting a coin in half means the two halves are both heads and tails until someone looks at one half. It is just ridiculous nonsense. Polarization of spin, there is not difference.

Alchemistry has more merit that this quantum entanglement nonsense. At least we really can turn lead into gold.



Science isn't about what YOU want it to look like, it's about the results of experiments.
Skeptic_Heretic
5 / 5 (1) May 21, 2010
Skeptic, granted the Heisenberg Uncertainty Principle places limits on observations in the micro world. But that is by no means proof something is in both states until it is examined anymore than my two coin halves are both heads and tails until someone picks one up and looks at it.

Ok, but you're ignoring the rest of what I said. The HUP isn't jsut a statement of measure, it's an observation of action. Unobserved particles do not have a spacial dimension so they exist EVERYWHERE in ALL STATES. The effects of which are determined by the probability observed indirectly within QM. It's definitively observed and repeatably proved.
Noumenon
4.5 / 5 (54) May 21, 2010
@Question, The Schrodinger cat thing was designed to magnify the measurement problem to the point of absurdity, as Schrodinger admitted it was silly. It's just an analogy. To complete it, I wouldn't say the cat is both alive and dead, I would say the concept of alive or dead requires and involves an observer,... I.e. an electron is a wave or a particle only in reference to a measurement upon it,.. prior to that it is unconceptualized as a "thing". Indeed, it is treated as a point particle in theories.

Physicists were dragged kicking and screaming into this weirdness. It is a epistemological issue that physics had to and is in need of overcoming.
CSharpner
5 / 5 (2) May 21, 2010
To those who think this is like putting two opposites in two boxes, then shipping them off, then both receivers opening the box and "instantly knowing" what the other has... you clearly do not understand QM nor this issue. The simplistic arguments you make are the same ones all newbs make when first getting into QM (including myself, at the time). I suggest you read QED (http://www.amazon...sr=1-1).

Also:
Delayed Choice Experiment:
http://www.bottom...oice.htm

Delayed Choice Quantum Eraser:
http://www.bottom...-web.htm
drel
5 / 5 (3) May 21, 2010

"Just because you don't know something does not make it both ways any more than splitting a coin in half means the two halves are both heads and tails until someone looks at one half. It is just ridiculous nonsense. Polarization of spin, there is not difference."

No it is not nonsense. Photons with unknown polarization behave differently in certain experiments than do photons of known polarization.
What you are claiming is that photons polarization is set but just not known. But experiments show that photons don't behave that way.

check out Alistair Rae's book
Quantum Physics:Illusion or Reality
Omit
not rated yet May 21, 2010
Maybe I am missing something....
To my understanding, you can only measure the spin... if two particals are entangled, and you measure the spin on one, you can know that the other is spinning in an oppisite way. At best, this may be able to be used as a means of encryption. The key to communicate this way would be able to control the spin of one of the entagled particals and measure the spin on the other at the same instant. This is still not possible as far as I know. (I could be wrong, has been a long time since I have studied this.)
Question
1 / 5 (3) May 21, 2010
Maybe I am missing something....
To my understanding, you can only measure the spin... if two particals are entangled, and you measure the spin on one, you can know that the other is spinning in an oppisite way. At best, this may be able to be used as a means of encryption. The key to communicate this way would be able to control the spin of one of the entagled particals and measure the spin on the other at the same instant. This is still not possible as far as I know. (I could be wrong, has been a long time since I have studied this.)


You are correct and that is why all this entanglement stuff is an excercise in futility.
It also proves that there is NO direct connection between these supposedly entangled particles.

CSharpner
5 / 5 (2) May 21, 2010
@Question: You really should read up on QED before you make outlandish claims that all the scientists that have been theorizing and experimenting with this for the last 100 years are wrong and you are right. Even the experiment in this article is based on this science.

Please explain to us why you are right and scientists for the last 100 years are wrong. In doing so, you'll need to explain the experimental results that side with QED. This, of course, requires you to become knowledgeable of QED. Once you become knowledgeable of it, your dissent will collapse like wave function. ;)

I suggest you read QED (http://www.amazon...=1-1).).

Also:
Delayed Choice Experiment:
http://www.bottom...oice.htm

Delayed Choice Quantum Eraser:
http://www.bottom...-web.htm
Noumenon
4.6 / 5 (54) May 21, 2010
Something I missed from article is that quantum teleportation requires a classical information channel, so I missed interpreted the above as FTL communication which it never claimed to be..
Question
1 / 5 (4) May 21, 2010
CSharpner: I do not think it is up to me to prove entanglement (beyond electromagnetically and gravitationally) does not exist, nobody can. It is up to your entanglement believer to prove it does. You have had about 100 years to do it and so far all I see for the efforts is a BIG goose egg, nothing.

daywalk3r
3.8 / 5 (16) May 21, 2010
Just a little nitpick..

"Entanglement" of two particles can become broken, quite "randomly", at virtualy any point durring its lifetime.. For example, by a chance (albeit very small) of collision with an external penetrating particle (e.g. cosmic ray).

And the best about it is, that you can't really know wether this allready happened or not! At least not faster, than the distance between the two particles divided by "c"..

"Uncertainity" at its best ;-D
fehmi_ben_njima
1 / 5 (1) May 21, 2010
hello i fave a simple question does this quantum comunication need a visible light to operate ( do i need to see alice to comunicate with her)
because the way that i understand quantum comunication is that it's a super wifi even if i am inside a cave i will have the cellular network
is that corect ?
DaveGee
not rated yet May 21, 2010
While I am in awe of and try desperately to understand how this quantum world behaves I'm more often lost than I am found... However, I'm very much reminded of a movie quote from my youth. One that seem to be apropos to my lack of understanding and though it funny enough to share...

"There are strange forces at work in your life. Magical ones that surround you. I don't understand them, but they frighten me. You have given me my life. The truth is I can never repay you. I have no honor, and never will have. I don't think you would kill me for being what I am, but better that than to return to Aquila. "


+2 for the first one to correctly identify the movie...
bluehigh
1 / 5 (2) May 21, 2010
Information is massless and can be conveyed without a carrier FTL. This technique is often (among other expresions) called deduction. Whether QE can be used to convey information FTL is an open question but allocating significant resources to enable a secure cypher indicates some very serious secrets. Certainly Ladyhawke not being one one them as the quote is readily available from Google.
LinkStarbureiy
5 / 5 (3) May 22, 2010
Again, time is a non-factor when it comes to quantum entanglement.
daywalk3r
3.6 / 5 (14) May 22, 2010
As far as quantum entanglement refers to reality, it is not certain; and as far as it is certain, it does not refer to reality.
There you go.. ;o)
ematiu
May 22, 2010
This comment has been removed by a moderator.
Noumenon
May 22, 2010
This comment has been removed by a moderator.
hylozoic
5 / 5 (1) May 22, 2010
To frame my point of view on this great thread, my academic research has been yet restricted to understanding quite a bit about memes and history. My sense of this subject comes from personal reading and from having friends who teach university chem and physics clarify things for me.
@ Csharpner -- "... your dissent will collapse like a wave function." Hahaha, well placed turn of phrase!
@Noumenon -- your positions and responses within this dialogue seem to be the most clear. Thank you for being patient enough to continue within the stream.

Help: Given the EWG model, can our development of instantaneous non-local exchange of information tell us anything about the nature of the non-collapsed wave-function universes? Theoretically?

P.S. Charles Fort would love the application, in this thread, of the term he (seemed to have) coined. Teleportation... and how!
CSharpner
5 / 5 (1) May 22, 2010
I do not think it is up to me to prove entanglement (beyond electromagnetically and gravitationally) does not exist, nobody can. It is up to your entanglement believer to prove it does. You have had about 100 years to do it and so far all I see for the efforts is a BIG goose egg, nothing.


WOW! You claim it doesn't exist?????
Physical experiments (of which I've posted 2... TWICE) side with it existing. I have no choice but to believe what physical experiments indicate. On the search bar on THIS site, I entered "entanglement" and this was the FIRST hit:

http://www.physor...388.html

There have been plenty of others.
http://www.physor...nglement

There are actually commercial products, available NOW that employ entanglement for quantum cryptography:
http://en.wikiped...tography

There is no debate. This is not like Al Gore claiming "the debate is over". There is no debate. QE exists and is utilized in commercial applications
MorituriMax
not rated yet May 22, 2010
If they ever get this to work reliably, it will mean absolutely secure crypto communications, with no possibility of man in the middle attacks.
Noumenon
4.5 / 5 (51) May 22, 2010
Help: Given the EWG model, can our development of instantaneous non-local exchange of information tell us anything about the nature of the non-collapsed wave-function universes? Theoretically?


If you are referring to the many-worlds interpretation in which there is no state reduction, but instead 'splitting' of universes you enter into metaphysical questions, because the presumption there is that the wavefunction is some kind of Real entity,... rather than a theoretical relation between observables.

Now someone could come along and say that my invocation of Kant's transcendental deduction in supporting Bohr's Copenhagen interpretation, is metaphysics. But, Kant's program was to define the scope of knowledge.

I have never heard of "memetics" although I've read Hofstadters popular book. Looks like a interesting concept,......
Noumenon
4.5 / 5 (52) May 22, 2010
......I could be off, but the way I regard the "the non-collapsed wavefunction" is as a theoretical net that is cast, that once Reality is caught (observation), it is subjected to conceptual mutilation (classical concepts), so that we can never come to know Reality as it is, in between observations, so the notion of many-worlds is pointless to me.
ddubia9
not rated yet May 23, 2010
As a layman, I would like to thank what I perceive to be credentialed contributions to this thread. This is VERY interesting stuff, at least from my perspective. This is the first physics thread I've ever visited on the internet (yeah, I'm old), and I was very happy to see the course of discussion. Can we just stick to science? Thanks in advance!
myrthryn
not rated yet May 23, 2010
This is quite fascinating stuff. I have been following this technology for a while. Always thought it would be fascinating if one could transmit information from the in/other side of a black hole.

Not to detract at all from the seriousness of this discussion; but if one wanted to add multiple reads to their data stream, one could just skip on the entangled particles and start using a stream of entangled cats. It is much easier to read the living/dead state of a cat, plus you get to do it nine times. ;-)
Raygunner
not rated yet May 25, 2010
Let me see, if I had two Q-readers separated by x distance and each containing a billion or so entangled pairs - would there be a way to "clock" these out in some fashion to get anything meaningful? There could be two boxes in each locale - a send and a receive. Well, probably not but I think if someone (or some technology) can look outside the box far enough there will be an angle to make this work - somehow. It may be a form of QM or something else. Sorry if I don't get this, not meant to irritate anyone. If I understand right, two entangled particles are simply mirror image clones that were "split" from the master - is that right? And the act of "looking" forces one to pick a state (or spin) to settle into, thereby forcing the other one to assume the opposite state - wherever the other one may be. Other than theory - how do we know for 100% that the particle is in superimposition unless we can observe it? And that very act causes the wave-function collapse? That's it - done here.
CSharpner
5 / 5 (1) May 25, 2010
Raygunner,

Good questions... The problem with trying to use this to transmit "classical" information faster than light (or backwards in time) is that you can't choose the quantum state on the sending side. If, after you've measured both sides, you then bring the measurements together (sub-luminally), you'll be able to confirm there's a correlation between the two... but not until then. But, until you do that, you'll see the measurements as nothing more than random data.

And yes, entangled photons in the experiments are generally created by splitting an original, single photon. Although, particles with mass have been entangled too, which do not originate from an original, single particle.

Check out these experiments. They may provide you a deeper answer than I can with a 500 character limit:

http://en.wikiped...periment

http://www.bottom...oice.htm
Skeptic_Heretic
5 / 5 (1) May 25, 2010
CS, correct in all respects except for one.

Since there is no "transmission" or travel within entanglement, you're not seinding information backwards in time. You're copying it to another location in spacetime. This is why it's really hard for most people to understand.
CSharpner
5 / 5 (1) May 25, 2010
Skeptic,

Correct. Though I use the term "transmit" loosely only to convey the idea of "something here at some time" correlates to "something there at some time".
Noumenon
4.5 / 5 (53) May 25, 2010
entangled photons in the experiments are generally created by splitting an original, single photon

..... another minor detail that may be of interest; A single photon cannot split into two. A higher frequency photon is absorbed and then two other photons of lower frequency are reemitted, at a later unpredictable time.
daywalk3r
3.7 / 5 (15) May 26, 2010
.... another minor detail that may be of interest; A single photon cannot split into two. A higher frequency photon is absorbed and then two other photons of lower frequency are reemitted, at a later unpredictable time.
Actually, it indeed is "splitting" when you look opon the whole "absorb-reemitt" process from the energy perspective. The re-emitted particles/waves originate from the very same "pack" of energy, which is split proportionally in the process, reduced by absorbtion/emitt losses depending on the resonant medium/mechanism used.

Not gonna comment on the "enpredictable time" part, as that is just asking for another "quantum vs classic" mammoth debate :)
daywalk3r
3.9 / 5 (15) May 26, 2010
If I understand right, two entangled particles are simply mirror image clones that were "split" from the master - is that right?
When it comes to "entanglated" matter particles, a more correct description would be that: they were "set" by a "split" master. And in the case of "entanglated" photons, they originate from a master that was "split".
And the act of "looking" forces one to pick a state (or spin) to settle into, thereby forcing the other one to assume the opposite state - wherever the other one may be.
Actually, that's what most like to believe it does, though they might aswell be synchronous for the whole durration. But by QM, doing 2 consecutive measurements on the samples is impossible (as the first measurement would instantly cause the "connection" between them to break), so this can not be verified..
daywalk3r
3.7 / 5 (12) May 26, 2010
Other than theory - how do we know for 100% that the particle is in superimposition unless we can observe it?
Well, we can not :) As by the latest and widely accepted QM interpretation, the only thing that you can be certain of is, that everything is uncertain (or respectively, that nothing is certain) ;-D

Blame the QM "fudge factor" for these misinterpretations :-P
Raygunner
5 / 5 (1) May 27, 2010
Thank you for your comments daywalk3r, and all of the others too. I think I have a limited understanding now - as flawed as it may be. And you've added some clarity in dealing with the murky QM fudge:^) Personally I don't think the Universe (as if it cares what we think) is going to go out of its way to muck things up a lot though. Sometimes we can't see those nuggets of truth because it seems folks are trying to force certain concepts that don't belong, or try to read more into things than are really there, and can't see the forest because of the trees. There are some important concepts missing. Once the LHC experiments connects our reality to the quantum sea we are immersed in, maybe things will start to make better sense as pieces fall into place. After all, we are trying to peel back reality's blanket and peer underneath. It's pretty awesome just trying to imagine what will be there. As long as it's not bedbugs...
altino
1 / 5 (1) May 27, 2010
Are we talking about aether as free-space? Hum? No? So much words, that i get confused really bad.
Now,... you can also comment on my words if you like. Please.
CSharpner
May 28, 2010
This comment has been removed by a moderator.
Raygunner
5 / 5 (1) May 28, 2010
One last thing (yea right)... I thought I understood that the up or down spin of particle "A" can be forced using mag fields, lasers, etc. This in turn forces the entangled particle "B" on the far end to the opposite state. If these are sync'd (self contained pico-sec res timing - no transmitted sync pulse or link) and clocked/read out on a schedule, could you not in fact send info? Sure the far end is inverted but you already know that and correct for read-back. A series of 8 entangled particles could be made to read out 8 bit binary. With billions or quadrillions in a TX/RX pair it seems that this might work. I think the media or some other article got me started on this track and I really want to know the truth - such as it is. Maybe it was someone's wishful fantasy that I read. Heck maybe it was even Star Trek. If I need to be shot down, please shoot.
CSharpner
5 / 5 (1) May 28, 2010
I would have thought the same thing. One side (and weird and important note): The timing is irrelevant to when you make a change to your particle to when the "receiver" reads it. The other particle is going to have the opposite value regardless of whether the receiver measures it at the same time you mark yours, after you mark yours (and get this..) or BEFORE you mark yours. I don't know if you can force a particular spin or polarity, but there are other problems involved. One of which is your receiving station will be receiving hits from stray particles and they won't know which are stray and which aren't. Also, as for the transmission of photons from the photon source.. the timing is also random. So, you need to make timing notes of each time you mark a particle and the receiver notes the timing of each received particle. THEN you both compare timing notes (the coincidence counter) to determine which received particles pair with "sent" particles. It seems there's always a catch.
Raygunner
not rated yet May 28, 2010
I think this is Nature's way of saying fugetaboutit!
Or it's just part of another quantum puzzle that you just have to pick at until you find a way to work it out. You are right CSharpner - the more you try the harder it gets. Maybe this is related to the holographic universe concept - the closer you look the fuzzier it becomes, like the grain in a piece of film. Are these parts of the same thing, a Quantum Holographic effect? I think we are running out of comments here.