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Sustained, high-fidelity quantum teleportation

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Re: Sustained, high-fidelity quantum teleportation

#51

Post by edge17 »

pontus wrote: post #38
junon wrote: post #20

Earlier quoted context omitted.

This makes zero sense. If the information must be conveyed classically anyway, what's the point?

Great question! This gets to the heart of why quantum teleportation has any value at all. So, before QM there was already a sense in which you could teleport an object: simply measure its state perfectly and send that information to another location and have them reconstruct that state particle by particle. In principle the new system would be indistinguishable from the original system and you could claim that you've…

Maybe I'm dense, but I still don't understand. The cloning explanation made sense to me, but to the original question - how does the recipient know the message is done being sent without the sender picking up the phone and calling the recipient...?

i.e. Is there some equivalent of a termination code/header sort of thing that the recipient is looking for in the 'bit stream' or whatever? Or am I not even thinking about this in terms of the right analogy?

edit: Thank btw, this comment was fascinating to me.

Re: Sustained, high-fidelity quantum teleportation

#52

Post by darau1 »

pontus wrote: post #38
junon wrote: post #20

Earlier quoted context omitted.

This makes zero sense. If the information must be conveyed classically anyway, what's the point?

Great question! This gets to the heart of why quantum teleportation has any value at all. So, before QM there was already a sense in which you could teleport an object: simply measure its state perfectly and send that information to another location and have them reconstruct that state particle by particle. In principle the new system would be indistinguishable from the original system and you could claim that you've…

So we'd still be limited by the speed of classical communication in sending the object's state to the new location? I hope I'm understanding this correctly.

Re: Sustained, high-fidelity quantum teleportation

#53

Post by up6w6 »

Quantum teleportation cant transport data faster than light, but something very similar which looks more useful in terms of daily needs is superdense coding [0]. Basically you could encode two bits as one qubit, which looks like some type of "physical compression" and the algorithm is almost the same as teleportation.

[0]: https://en.wikipedia.org/wiki/Superdense_coding

Re: Sustained, high-fidelity quantum teleportation

#54

Post by bluesign »

cambalache wrote: post #14
Mizza wrote: post #8

Earlier quoted context omitted.

Any chance that communication could happen _before_ the measurement? Entangle some matter, give half of it to the space team and then have inter-stellar walkie talkies?

No communication is possible BUT, I have this toy scenario where a "quasi-communication" may be possible in FTL speed. "2 generals command 2 armies hundreds of km apart. They want to attack a common enemy, there are 2 options, A) And all-front attack. B) From the flanks. The generals want the plans to remain uncertain until the last second before the attack. So from an intermediate point, they send two "entangled coi…

Sorry but this example doesn't make sense, how it is faster than light?

Re: Sustained, high-fidelity quantum teleportation

#55

Post by pontus »

darau1 wrote: post #52
pontus wrote: post #38

Earlier quoted context omitted.

Great question! This gets to the heart of why quantum teleportation has any value at all. So, before QM there was already a sense in which you could teleport an object: simply measure its state perfectly and send that information to another location and have them reconstruct that state particle by particle. In principle the new system would be indistinguishable from the original system and you could claim that you've…

So we'd still be limited by the speed of classical communication in sending the object's state to the new location? I hope I'm understanding this correctly.

Yes, that's correct

Re: Sustained, high-fidelity quantum teleportation

#56

Post by ajuc »

up6w6 wrote: post #53

Quantum teleportation cant transport data faster than light, but something very similar which looks more useful in terms of daily needs is superdense coding [0]. Basically you could encode two bits as one qubit, which looks like some type of "physical compression" and the algorithm is almost the same as teleportation. [0]: https://en.wikipedia.org/wiki/Superdense_coding

Isn't that the same as just using 4 voltages (or any other analog property) instead of 2 to encode 2 bits instead of 1?

Qbits are analog so it's no surprise it can be done with them as well.

Flash memory already does that in classical chips. There's nothing preventing you from going further - 8 voltages for 3 bits etc.

Re: Sustained, high-fidelity quantum teleportation

#57

Post by tomrod »

pontus wrote: post #44
sebmellen wrote: post #42

Earlier quoted context omitted.

Very interesting. If I understand correctly, does this mean cloning is a functionally impossible task? I've always been entertained by the paradoxes where someone is teleported ala Michael Crichton's Timeline , and is then (due to some glitch) "duplicated", leading to interesting quandaries about "who is who". If Penrose is right about consciousness [0], this means all these fantastical paradoxes are just fantasy, ri…

Correct, cloning in even the simplest sense of a single particle state (let alone a whole human) is impossible in quantum mechanics.

It sounds like state send is partial using the "phone" analogy.

Can there be triplicates of entanglement?

Re: Sustained, high-fidelity quantum teleportation

#58

Post by comfyinnernet »

sebmellen wrote: post #42
pontus wrote: post #38

Earlier quoted context omitted.

Great question! This gets to the heart of why quantum teleportation has any value at all. So, before QM there was already a sense in which you could teleport an object: simply measure its state perfectly and send that information to another location and have them reconstruct that state particle by particle. In principle the new system would be indistinguishable from the original system and you could claim that you've…

Very interesting. If I understand correctly, does this mean cloning is a functionally impossible task? I've always been entertained by the paradoxes where someone is teleported ala Michael Crichton's Timeline , and is then (due to some glitch) "duplicated", leading to interesting quandaries about "who is who". If Penrose is right about consciousness [0], this means all these fantastical paradoxes are just fantasy, ri…

I don't think you would need exact duplication for these situations to arise.

Re: Sustained, high-fidelity quantum teleportation

#59

Post by colechristensen »

darau1 wrote: post #52
pontus wrote: post #38

Earlier quoted context omitted.

Great question! This gets to the heart of why quantum teleportation has any value at all. So, before QM there was already a sense in which you could teleport an object: simply measure its state perfectly and send that information to another location and have them reconstruct that state particle by particle. In principle the new system would be indistinguishable from the original system and you could claim that you've…

So we'd still be limited by the speed of classical communication in sending the object's state to the new location? I hope I'm understanding this correctly.

Yes, to achieve entanglement in the first place you have to either do something to two objects at a distance and that action can’t exceed the speed of light (and often is light) or you have to entangle two objects and then move them to their destination.

Teleportation is achieved by doing a specific action on one and then communicating to the other to do a specific action to the other.

In no case can information be transmitted faster than light.

Re: Sustained, high-fidelity quantum teleportation

#60

Post by maxerickson »

mrtesthah wrote: post #43
pontus wrote: post #38

Earlier quoted context omitted.

Great question! This gets to the heart of why quantum teleportation has any value at all. So, before QM there was already a sense in which you could teleport an object: simply measure its state perfectly and send that information to another location and have them reconstruct that state particle by particle. In principle the new system would be indistinguishable from the original system and you could claim that you've…

It sounds like start trek’s transporter beams may be more accurately described than we thought.

They repeatedly treat the pattern like data.

Riker splits, Tuvix!, the one where the other doctor ages and gets de-aged in the transporter, the one where Scotty is stored in it for decades, etc.

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