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Researchers quantum teleport particle of light six kilometres

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Re: Researchers quantum teleport particle of light six kilometres

#131

Post by semi-extrinsic »

stephengillie wrote: post #103
TheRealPomax wrote: post #83

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 po…

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.

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

Re: Researchers quantum teleport particle of light six kilometres

#132

Post by jomamaxx »

sebringj wrote: post #110

Does modifying the state of one entangled particle then destroy the link between them? If it does, then how can you continually communicate without distance being a factor as you'll have to resupply? I hope it doesn't or there is some work around or I simply am completely asking the wrong question.

Yes, the observation destroys the entanglement.

The communication does not really happen between the state that is 'teleported' - you still have to manually send the photons 6km or whatever. But - very crudely - you can pass information from one entangled particle to it's pair 6km away and observe the results.

So, you still have to have a fiber or whatever.

Also - because it's all probabilistic and you don't know for sure if it worked in any given instance, you still need another classical channel to communicate information about what was passed in the first place.

Re: Researchers quantum teleport particle of light six kilometres

#134

Post by jomamaxx »

kraftman wrote: post #8

>> Dark fibre, so named because of its composition — a single optical cable with no electronics or network equipment on the alignment — doesn’t interfere with quantum technology Isn't dark fibre either unlit capacity or leased fibres?

Dark fibre I think is used simply to refer to fibre that's not being used at a given time. So I guess it can mean different things.

Re: Researchers quantum teleport particle of light six kilometres

#135

Post by johncolanduoni »

TheRealPomax wrote: post #83

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 po…

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

Re: Researchers quantum teleport particle of light six kilometres

#136

Post by das3ddddddd »

duaneb wrote: post #99
TheRealPomax wrote: post #83

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 po…

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

This is key and why most people don't understand why the name quantum teleportation really is appropriate.

And when you consider the only difference between two particles is the information state they are in. And that you do teleport the information. The name is not misleading.

Re: Researchers quantum teleport particle of light six kilometres

#137

Post by johncolanduoni »

Ciantic wrote: post #118
TheRealPomax wrote: post #83

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 po…

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.

You're thinking of measuring entangled pairs to produce consistent streams of random classical bits. That is not what quantum teleportation is, although both do use EPR pairs. Their experiment is still bound by the speed of light because they are in fact communicating a full, pre-determined quantum state, not random bits.

Re: Researchers quantum teleport particle of light six kilometres

#138

Post by Dylan16807 »

Ciantic wrote: post #125
das3ddddddd wrote: post #123

Earlier quoted context omitted.

No, you're thinking about quantum entanglement.

Yes, and as others pointed out below, this is essentially entanglement.

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.

Re: Researchers quantum teleport particle of light six kilometres

#139

Post by das3ddddddd »

semi-extrinsic wrote: post #131
stephengillie wrote: post #103

Earlier quoted context omitted.

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.

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

The purpose of quantum teleportation is the teleportation of quantum information. Teleportation is not necessary to the creation of a secure communication channel.

Re: Researchers quantum teleport particle of light six kilometres

#140

Post by Dylan16807 »

ethanbond wrote: post #120
radicaldreamer wrote: post #114

Earlier quoted context omitted.

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.

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 transmi…

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.
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