Researchers quantum teleport particle of light six kilometres • Hacker News Board

Re: Researchers quantum teleport particle of light six kilometres

#111

Post by AgentME » Wed, Sep 21, 2016, 5:51 PM UTC

MichaelBurge wrote: post #79

lisper wrote: post #73

Earlier quoted context omitted.

It's not "fairly certain", it's absolutely certain. http://blog.rongarret.info/2014/12/quantum-teleportation-dem... (Also submitted to HN: https://news.ycombinator.com/item?id=12549728 )

What if you destroy the entanglement by destroying one of the entangled particles? You can't do this by shooting it with a particle accelerator, or else the entanglement infects whatever you hit it with; but you could use an intense field like sending a photon into a black hole or an atom into a neutron star to be ripped apart. Is there a rule for describing the entanglement of the resulting constituent particles wit…

Nothing you do to one of the particles is going to noticeably affect anything about the other particle's measurement by itself. Any link between the particles is only apparent by comparing both the measurements together.

Imagine you had a machine print out two envelopes with the same random number inside. You and a friend take these envelopes and each go 1 lightyear in separate directions. When you open your envelope, you will instantly know what number was in your friend's envelope. There's no usable FTL communication here. Burning your envelope won't communicate anything FTL to your friend. This just means that when you meet up again, he'll say he believes that you got a 7, and you'll say that he's wrong because you threw away the entanglement first by burning your envelope without looking at it.

There are plenty of interesting quirks about about quantum entanglement that this model doesn't contain, but it should cover the lack of FTL communication potential correctly.

Re: Researchers quantum teleport particle of light six kilometres

#112

Post by zeveb » Wed, Sep 21, 2016, 5:53 PM UTC

bostonpete wrote: post #98

lisper wrote: post #82

Earlier quoted context omitted.

It is as certain as anything in science. Yes, QM is incomplete, but it places hard constraints on the space of possible completions, and none of them allow FTL communications. FTL would break not only QM and relativity, but causality: it would allow you to send information backwards in time.

It seems to me that's exactly what an alien trying to keep us in the dark would say...

> It seems to me that's exactly what an alien trying to keep us in the dark would say...

Well, Lisp is secret alien technology: http://lispers.org/

Re: Researchers quantum teleport particle of light six kilometres

#113

Post by tomrod » Wed, Sep 21, 2016, 5:54 PM UTC

jdmichal wrote: post #28

I posted this in a duplicate thread: For those thinking that this is a step towards faster-than-light (FTL) communication: As far as I know it's fairly certain that quantum entanglement will not allow for FTL communication. Basic principle is that while measurements between both sides will be correlated, it's not possible to tell how they are correlated until both sides compare measurements. https://en.wikipedia.org/…

Why couldn't you create a functional telegraph through light shift pulsing? One particle would be insufficient, but a mole of particles...

Would that break the entanglement?

Re: Researchers quantum teleport particle of light six kilometres

#114

Post by radicaldreamer » Wed, Sep 21, 2016, 5:55 PM UTC

aji wrote: post #96

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…

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

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.

Re: Researchers quantum teleport particle of light six kilometres

#115

Post by [deleted] » Wed, Sep 21, 2016, 5:55 PM UTC

raverbashing wrote: post #109

duaneb wrote: post #99

Earlier quoted context omitted.

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

What do you mean by that?

[deleted]

Re: Researchers quantum teleport particle of light six kilometres

#116

Post by cristianpascu » Wed, Sep 21, 2016, 5:56 PM UTC

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.

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.

Re: Researchers quantum teleport particle of light six kilometres

#117

Post by javajosh » Wed, Sep 21, 2016, 5:57 PM UTC

drostie wrote: post #104

javajosh wrote: post #92

Earlier quoted context omitted.

> Since this process converts quantum information to classical information (a digital or analog signal), we know that it must lose information. Only by making many measurements can we infer statistical properties of the entire quantum state. This is exactly what happens with the two-slit experiment. Wow, I've never heard it explained that way. That's brilliant - did you come up with it? Interference patterns are the…

Are you still comfortable with this explanation if the photons are released with a 1-second gap between them and the tally is visibly shown building up into the interference effect on a computer screen? "Interfering with each other at an enormous rate" might mislead you a bit; neither "each other" nor "enormous rate" is particularly important in the double-slit interference pattern.

Actually, you can't know this until you get a lot of measurements to see the pattern. E.g. if you just put one photon through you get one dot, and you'd be hard pressed to infer anything from that. So in the end you still need a lot of measurements to detect interference.

Also I bet you could mess with the interference pattern by pulsing the light source. This would be the lesser known form of the Uncertainty principle, where energy and time are unknowable.

Re: Researchers quantum teleport particle of light six kilometres

#118

Post by Ciantic » Wed, Sep 21, 2016, 5:57 PM UTC

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.

Re: Researchers quantum teleport particle of light six kilometres

#119

Post by duaneb » Wed, Sep 21, 2016, 5:58 PM UTC

cristianpascu wrote: post #116

duaneb wrote: post #99

Earlier quoted context omitted.

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

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…

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?

Re: Researchers quantum teleport particle of light six kilometres

#120

Post by ethanbond » Wed, Sep 21, 2016, 5:59 PM UTC

radicaldreamer wrote: post #114

aji wrote: post #96

Earlier quoted context omitted.

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

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 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.