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Not quite as impressive when you know, and if you don't you should before opening this link, that "quantum teleportation" is not teleportation. It was a cool-so

Not quite as impressive when you know, and if you don't you should before opening this link, that "quantum teleportation" is not teleportation. It was a cool-sounding name at the time, but has nothing to do with sci-fi style teleportation: nothing disappears from one place and then shows up in another. "Quantum teleportation" is a process of information duplication using particles that already exist, and have been positioned such that there is enough distance between them that we can rule out direct interaction between them (that we know of given the current state of physics). Quantum teleportation is the process by which we then manipulate only the particles on one side of the distance divide, such that particles on the other side "end up" reflecting the same state that the ones we manipulated were. Although "ending up" is probably the wrong term, because we use particles in special states of which we already know they're entangled, then split them up (which does not cancel entanglement) and then we make use of their entanglement property: running an algorithm involving particles on one side should yield the exact same result as running the same algorithm on the other side, so a much more interesting algorithm is one that you run on one side in one way, and on the other in a different way, to effect a "data copy" without ever actually copying data (and very much without any kind of teleportation. The fact that you run your process with "the same particle" is the special part. Being able to even have two particles that are literally the same is a pretty bizarre bit of physics)

aji 10y ago
right, "quantum teleportation" is a woefully misleading name, however this is still an impressive advancement and quantum teleportation will play a key role in wide-area quantum information networks
- radicaldreamer 10y ago
  This is probably also why SETI-like projects turn up nothing. It's likely that almost no advanced civilizations are using radio waves for communication.
  - ethanbond 10y ago
    I'm only a layman who's mildly interested in this, but this contradicts my understanding... Someone correct me if I'm wrong here. You can't communicate with quantum teleportation. It sends random "information" (not information at all), because you can't control how the quantum waveform collapses. So you have to collapse the waveform, create a key that encodes your collapsed form to the information you want to transmit, and then transmit that key slower than light i.e. with radio. I guess you could argue that since the keys themselves are also indistinguishable from noise, we wouldn't detect slower-than-light key transmission either, though.
    - Dylan16807 10y ago
      Modern radio signals are pretty close to noise anyway. You increase capacity by going to the very limit of what your receiver can distinguish. The only thing you can measure from a distance is that certain frequency ranges have more power than background.
    - roywiggins 10y ago
      So far as I know, that's correct. There's even a handy theorem that states this pretty unequivocally! > it is not possible for one observer, by making a measurement of a subsystem of the total state, to communicate information to another observer. The theorem is important because, in quantum mechanics, quantum entanglement is an effect by which certain widely separated events can be correlated in ways that suggest the possibility of instantaneous communication. The no-communication theorem gives conditions under which such transfer of information between two observers is impossible. https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem
    - aji 10y ago
      you can't "communicate", but it would be useful for qubits in one quantum computer to be sent to another quantum computer without physically moving the qubit. that was what I meant by wide-area quantum information networks
      - 10y ago
- elboru 10y ago
  Since nobody has mentioned it, maybe I didn't understand the implications, but does this mean there is a chance in the future we won't have "bandwidth"? I could replicate data from a server into my personal computer instantly?
  - TheRealPomax 10y ago
    Not really. Not unless you and whomever you were getting data from shared entangled particle pairs. While this is a real thing already, some banks use this setup for quantum encryption, it's probabilistic (particles can stop being entangled, so you have to run checks against a series of them and then decide that p>0.999 is good enough for instance) and the owners of each particle is regulated. There is no QT without first making sure two parties each hold half of an entangled pair, and then make sure they both use the same particle for running the QT algorithm against.
  - aji 10y ago
    quantum teleportation is not instant, since the information about the particle's quantum state is still sent over a classical channel
duaneb 10y ago
At the subatomic level, is there any real difference between information and a "thing"? Seems mostly philosophical and arbitrary at that point.
- raverbashing 10y ago
  What do you mean by that?
  - deleted 10y ago
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- cristianpascu 10y ago
  Information is a mental concept. That is, it's based on the someone knowing the range of possibilities of a certain state of affairs involving things/entities. For instance the top face of a dice. You know there are 6 possibilities, but at the moment, there's only one face at the top. Same with quantum particles, we attach properties to them, and these properties can have one value out of many. Measuring the specific value yields 'information' because you put that value in the context of the possible values you could find. The particle sent you a message, its properties. But being related to reality, it's easy to be confused or rightfully associated with being a thing. I'd say that it's superposition of epistemology and ontology. You can't really separated to knower from the known.
  - duaneb 10y ago
    Sure, but everything qualitative is information. What remains? Is there any other way to think about reality than information? Seems kind of silly to pull apart information as somehow separate or lesser than reality. Saying "real teleportation" is somehow different than "just information" is nonsensical. It's like saying with quantum teleportation that the two particles aren't "really" entangled, they just have the same state. Well if you can't distinguish the state, what distinguishes them? They're literally the same until something distinguishes them. Or, to put it another way, "just" information teleporting isn't any less exciting. "real" teleportation doesn't hold up to much thought anyway; it's very difficult to ground it in physical terms. Is there much point assuming people think about teleportation that way?
stephengillie 10y ago
This is, very confusingly, "teleportation of the quantum state". Not unlike how merging a pull request is "teleporting the software state of your repo", but instantaneously. Essentially this is just entanglement at 6 kilometers, described by a blustery article.
- semi-extrinsic 10y ago
  No, "quantum teleportation" is a specific technical term for a type of communication that involves both entanglement and a classical communication channel to together create a secure communication channel. https://en.wikipedia.org/wiki/Quantum_teleportation https://en.wikipedia.org/wiki/Quantum_teleportation
  - das3ddddddd 10y ago
    The purpose of quantum teleportation is the teleportation of quantum information. Teleportation is not necessary to the creation of a secure communication channel.
- smsm42 10y ago
  Not sure about "instantaneously" part. It's more like I send you a pull request and then I apply it to my repo and tell you to apply it to your repo and you get your repo in certain state which I knew upfront. Repo state teleportation! Yeah, it know it's not exactly that either, but it's about as magical as that, AFAIU. Which doesn't say it's not useful - ability to merge pulls and get all the repos in certain state is hugely useful - but calling it "teleportation" implying that we're on the verge of being beamed up and down like StarTrek characters sounds a bit more pompous than warranted.
deleted 10y ago
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Ciantic 10y ago
It's easier to think these as random number generators seeded with same value, taken six kilometers apart from each other, and then fetching values from them. No data is transmitted when fetching values from these.
- das3ddddddd 10y ago
  No, you're thinking about quantum entanglement.
  - Ciantic 10y ago
    Yes, and as others pointed out below, this is essentially entanglement.
    - deleted 10y ago
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    - Dylan16807 10y ago
      This is an effect that uses entanglement to move the state of one particle to a different particle. You're describing only entanglement, so that's only half the puzzle. And you're describing entanglement in a misleading way. The most important part of entanglement is that you can't model it as two particles sharing secret data. When you touch one, you affect the output of the other. And this happens faster than light. It still looks random on each end, but once you combine the measurements you can see patterns.
      - arcticfox 10y ago
        Is their any layman's physics explanation of how this works? Obviously you can't transmit information, but one particle can affect the other at distance faster than the speed of light? My sense was that quantum physics basically makes sense if you go really small and have an understanding of how the particles interact. But entanglement is weird, because somehow there's also a mechanism for them to interact at distance? (I know, I could try to look it up, but hopefully other people here have the same silly question)
das3ddddddd 10y ago
"nothing disappears from one place and then shows up in another." This is false. The quantum data is completely destroyed at the entry point and it shows up at the end point.
johncolanduoni 10y ago
You've compounded their lazy science reporting by making quite a few mistakes yourself in your description: 1. There is no duplication or copying of information, the original particle's state is destroyed. Copying is impossible when dealing with general quantum states[1]. (You may be thinking of measuring an entangled pair to randomly produce a stream of classical bits on each side that is the precise inverse of what is produced on the other side. This is not quantum teleportation.) 2. There is a very real notion of teleportation here, in that you take a particle with a quantum state A, and manipulate it in such a way that it stays where it is while causing a particle of the same type in a different place to be in precisely the state A, without actually moving the first particle to the second location. Yes, it's not likely to ever be used to beam anybody anywhere, but for photons it's very much like teleportation. 3. The two particles are not "literally the same", or even figuratively the same. The particles when measured will result in the other particle ending up in the opposite of the measured state, and this inversion persists even if we do operations that preserve the quantum state. [1]: https://en.wikipedia.org/wiki/No-cloning_theorem https://en.wikipedia.org/wiki/No-cloning_theorem
- TheRealPomax 10y ago
  "Duplication" was the wrong term, I should have said "destructive-read/write", which I did in another comment. 2. There is no teleportation in the common man, sci-fi interpretation. In order to effect the information transferral we need three times as many particles as we're transferring the information of. Per particle whose state is to be tranferred, we need two entangled particles and a target particle. To translate that to the "teleporting a thing" case, if you were to teleport a cake, you'd need a cake, two (entangled) cake-equivalent mass collections, and a target "generic particle collection" to be turned into "your cake" after running the QT algorithm. It's only teleportation if you pretend that triplicate wasted-once-used mass isn't there, which we can't do: it's there, and this is QT, not 'regular' teleportation (ignoring the fact that there is no such thing outside of works of fiction =) 3. fair enough, I simplified that the wrong way. https://en.wikipedia.org/wiki/Quantum_entanglement https://en.wikipedia.org/wiki/Quantum_entanglement and https://en.wikipedia.org/wiki/Quantum_entanglement#Applications https://en.wikipedia.org/wiki/Quantum_entanglement#Applicati... might work better as highlighting links here, although something like "Quantum Computation and Quantum Information" by Nielsen and Chuang would be a much better reference.
owaislone 10y ago
Isn't that how actual sci-fi teleportation would work behind the scenes as well? Basically, if I wanted to teleport myself from one city to another. I'd actually die and disappear, and an exact copy myself would be created instantly in the other city. It would be teleportation for the rest of the world but for me it would be death.
- dragonwriter 10y ago
  > Isn't that how actual sci-fi teleportation would work behind the scenes as well? Depends. Some versions are materialize/dematerialize, some, IIRC, are basically traversable short-lived artificial wormholes.
- TheRealPomax 10y ago
  If they relied on quantum teleportation: no, not in the slightest. In order to QT a particle (explicitly not using the verb "teleport" here, because it's a very different thing) you need three additional particles for every particle you're QTing. A pair of entangled particles that act as your fascilitator, and a spare particle on the other end to take on the information state of the one you're QTing. So unless your sci-fi teleporter comes with a massive amount of pre-entangled particles half of which you have, half of which "they" have, plus an equivalent-mass-worth of particles to accept the teleportation subject, it's still just science fiction.
  - deleted 10y ago
    [deleted]
M_Grey 10y ago
You do understand that this has applications that are quite useful though, right? I understand that you're objecting to the terminology, but the actual process is going to be a necessary part of any large-scale "quantum internet", and needs to be mastered.
echelon 10y ago
Dumb, layman question: would it be possible to "quantum teleport" state information from the future? I've seen articles that describe "sampling" entangled particles statistically without disturbing the entanglement (I assume these are large sets of particles). I've also seen articles that describe properties being affected by future states of the system as the wave function collapses. (Forgive my lack of citation, and poor recollection / understanding.) Could properties like this be used in conjunction?
ButchC 10y ago
I found this Veritasium video nice for explaining quantum entanglement at a super basic level. https://www.youtube.com/watch?v=ZuvK-od647c https://www.youtube.com/watch?v=ZuvK-od647c

aji 10y ago

right, "quantum teleportation" is a woefully misleading name, however this is still an impressive advancement and quantum teleportation will play a key role in wide-area quantum information networks

radicaldreamer 10y ago
This is probably also why SETI-like projects turn up nothing. It's likely that almost no advanced civilizations are using radio waves for communication.
- ethanbond 10y ago
  I'm only a layman who's mildly interested in this, but this contradicts my understanding... Someone correct me if I'm wrong here. You can't communicate with quantum teleportation. It sends random "information" (not information at all), because you can't control how the quantum waveform collapses. So you have to collapse the waveform, create a key that encodes your collapsed form to the information you want to transmit, and then transmit that key slower than light i.e. with radio. I guess you could argue that since the keys themselves are also indistinguishable from noise, we wouldn't detect slower-than-light key transmission either, though.
  - Dylan16807 10y ago
    Modern radio signals are pretty close to noise anyway. You increase capacity by going to the very limit of what your receiver can distinguish. The only thing you can measure from a distance is that certain frequency ranges have more power than background.
  - roywiggins 10y ago
    So far as I know, that's correct. There's even a handy theorem that states this pretty unequivocally! > it is not possible for one observer, by making a measurement of a subsystem of the total state, to communicate information to another observer. The theorem is important because, in quantum mechanics, quantum entanglement is an effect by which certain widely separated events can be correlated in ways that suggest the possibility of instantaneous communication. The no-communication theorem gives conditions under which such transfer of information between two observers is impossible. https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem
  - aji 10y ago
    you can't "communicate", but it would be useful for qubits in one quantum computer to be sent to another quantum computer without physically moving the qubit. that was what I meant by wide-area quantum information networks
    - 10y ago
elboru 10y ago
Since nobody has mentioned it, maybe I didn't understand the implications, but does this mean there is a chance in the future we won't have "bandwidth"? I could replicate data from a server into my personal computer instantly?
- TheRealPomax 10y ago
  Not really. Not unless you and whomever you were getting data from shared entangled particle pairs. While this is a real thing already, some banks use this setup for quantum encryption, it's probabilistic (particles can stop being entangled, so you have to run checks against a series of them and then decide that p>0.999 is good enough for instance) and the owners of each particle is regulated. There is no QT without first making sure two parties each hold half of an entangled pair, and then make sure they both use the same particle for running the QT algorithm against.
- aji 10y ago
  quantum teleportation is not instant, since the information about the particle's quantum state is still sent over a classical channel

duaneb 10y ago

At the subatomic level, is there any real difference between information and a "thing"? Seems mostly philosophical and arbitrary at that point.

raverbashing 10y ago
What do you mean by that?
- deleted 10y ago
  [deleted]
cristianpascu 10y ago
Information is a mental concept. That is, it's based on the someone knowing the range of possibilities of a certain state of affairs involving things/entities. For instance the top face of a dice. You know there are 6 possibilities, but at the moment, there's only one face at the top. Same with quantum particles, we attach properties to them, and these properties can have one value out of many. Measuring the specific value yields 'information' because you put that value in the context of the possible values you could find. The particle sent you a message, its properties. But being related to reality, it's easy to be confused or rightfully associated with being a thing. I'd say that it's superposition of epistemology and ontology. You can't really separated to knower from the known.
- duaneb 10y ago
  Sure, but everything qualitative is information. What remains? Is there any other way to think about reality than information? Seems kind of silly to pull apart information as somehow separate or lesser than reality. Saying "real teleportation" is somehow different than "just information" is nonsensical. It's like saying with quantum teleportation that the two particles aren't "really" entangled, they just have the same state. Well if you can't distinguish the state, what distinguishes them? They're literally the same until something distinguishes them. Or, to put it another way, "just" information teleporting isn't any less exciting. "real" teleportation doesn't hold up to much thought anyway; it's very difficult to ground it in physical terms. Is there much point assuming people think about teleportation that way?

stephengillie 10y ago

This is, very confusingly, "teleportation of the quantum state". Not unlike how merging a pull request is "teleporting the software state of your repo", but instantaneously. Essentially this is just entanglement at 6 kilometers, described by a blustery article.

semi-extrinsic 10y ago
No, "quantum teleportation" is a specific technical term for a type of communication that involves both entanglement and a classical communication channel to together create a secure communication channel. https://en.wikipedia.org/wiki/Quantum_teleportation https://en.wikipedia.org/wiki/Quantum_teleportation
- das3ddddddd 10y ago
  The purpose of quantum teleportation is the teleportation of quantum information. Teleportation is not necessary to the creation of a secure communication channel.
smsm42 10y ago
Not sure about "instantaneously" part. It's more like I send you a pull request and then I apply it to my repo and tell you to apply it to your repo and you get your repo in certain state which I knew upfront. Repo state teleportation! Yeah, it know it's not exactly that either, but it's about as magical as that, AFAIU. Which doesn't say it's not useful - ability to merge pulls and get all the repos in certain state is hugely useful - but calling it "teleportation" implying that we're on the verge of being beamed up and down like StarTrek characters sounds a bit more pompous than warranted.

deleted 10y ago

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Ciantic 10y ago

It's easier to think these as random number generators seeded with same value, taken six kilometers apart from each other, and then fetching values from them. No data is transmitted when fetching values from these.

das3ddddddd 10y ago
No, you're thinking about quantum entanglement.
- Ciantic 10y ago
  Yes, and as others pointed out below, this is essentially entanglement.
  - deleted 10y ago
    [deleted]
  - Dylan16807 10y ago
    This is an effect that uses entanglement to move the state of one particle to a different particle. You're describing only entanglement, so that's only half the puzzle. And you're describing entanglement in a misleading way. The most important part of entanglement is that you can't model it as two particles sharing secret data. When you touch one, you affect the output of the other. And this happens faster than light. It still looks random on each end, but once you combine the measurements you can see patterns.
    - arcticfox 10y ago
      Is their any layman's physics explanation of how this works? Obviously you can't transmit information, but one particle can affect the other at distance faster than the speed of light? My sense was that quantum physics basically makes sense if you go really small and have an understanding of how the particles interact. But entanglement is weird, because somehow there's also a mechanism for them to interact at distance? (I know, I could try to look it up, but hopefully other people here have the same silly question)

das3ddddddd 10y ago

"nothing disappears from one place and then shows up in another." This is false. The quantum data is completely destroyed at the entry point and it shows up at the end point.

johncolanduoni 10y ago

You've compounded their lazy science reporting by making quite a few mistakes yourself in your description: 1. There is no duplication or copying of information, the original particle's state is destroyed. Copying is impossible when dealing with general quantum states[1]. (You may be thinking of measuring an entangled pair to randomly produce a stream of classical bits on each side that is the precise inverse of what is produced on the other side. This is not quantum teleportation.) 2. There is a very real notion of teleportation here, in that you take a particle with a quantum state A, and manipulate it in such a way that it stays where it is while causing a particle of the same type in a different place to be in precisely the state A, without actually moving the first particle to the second location. Yes, it's not likely to ever be used to beam anybody anywhere, but for photons it's very much like teleportation. 3. The two particles are not "literally the same", or even figuratively the same. The particles when measured will result in the other particle ending up in the opposite of the measured state, and this inversion persists even if we do operations that preserve the quantum state. [1]: https://en.wikipedia.org/wiki/No-cloning_theorem https://en.wikipedia.org/wiki/No-cloning_theorem

TheRealPomax 10y ago
"Duplication" was the wrong term, I should have said "destructive-read/write", which I did in another comment. 2. There is no teleportation in the common man, sci-fi interpretation. In order to effect the information transferral we need three times as many particles as we're transferring the information of. Per particle whose state is to be tranferred, we need two entangled particles and a target particle. To translate that to the "teleporting a thing" case, if you were to teleport a cake, you'd need a cake, two (entangled) cake-equivalent mass collections, and a target "generic particle collection" to be turned into "your cake" after running the QT algorithm. It's only teleportation if you pretend that triplicate wasted-once-used mass isn't there, which we can't do: it's there, and this is QT, not 'regular' teleportation (ignoring the fact that there is no such thing outside of works of fiction =) 3. fair enough, I simplified that the wrong way. https://en.wikipedia.org/wiki/Quantum_entanglement https://en.wikipedia.org/wiki/Quantum_entanglement and https://en.wikipedia.org/wiki/Quantum_entanglement#Applications https://en.wikipedia.org/wiki/Quantum_entanglement#Applicati... might work better as highlighting links here, although something like "Quantum Computation and Quantum Information" by Nielsen and Chuang would be a much better reference.

owaislone 10y ago

Isn't that how actual sci-fi teleportation would work behind the scenes as well? Basically, if I wanted to teleport myself from one city to another. I'd actually die and disappear, and an exact copy myself would be created instantly in the other city. It would be teleportation for the rest of the world but for me it would be death.

dragonwriter 10y ago
> Isn't that how actual sci-fi teleportation would work behind the scenes as well? Depends. Some versions are materialize/dematerialize, some, IIRC, are basically traversable short-lived artificial wormholes.
TheRealPomax 10y ago
If they relied on quantum teleportation: no, not in the slightest. In order to QT a particle (explicitly not using the verb "teleport" here, because it's a very different thing) you need three additional particles for every particle you're QTing. A pair of entangled particles that act as your fascilitator, and a spare particle on the other end to take on the information state of the one you're QTing. So unless your sci-fi teleporter comes with a massive amount of pre-entangled particles half of which you have, half of which "they" have, plus an equivalent-mass-worth of particles to accept the teleportation subject, it's still just science fiction.
- deleted 10y ago
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M_Grey 10y ago

You do understand that this has applications that are quite useful though, right? I understand that you're objecting to the terminology, but the actual process is going to be a necessary part of any large-scale "quantum internet", and needs to be mastered.

echelon 10y ago

Dumb, layman question: would it be possible to "quantum teleport" state information from the future? I've seen articles that describe "sampling" entangled particles statistically without disturbing the entanglement (I assume these are large sets of particles). I've also seen articles that describe properties being affected by future states of the system as the wave function collapses. (Forgive my lack of citation, and poor recollection / understanding.) Could properties like this be used in conjunction?

ButchC 10y ago

I found this Veritasium video nice for explaining quantum entanglement at a super basic level. https://www.youtube.com/watch?v=ZuvK-od647c https://www.youtube.com/watch?v=ZuvK-od647c