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Sustained, high-fidelity quantum teleportation

news.fnal.gov

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Re: Sustained, high-fidelity quantum teleportation

#21

Post by ed25519FUUU »

junon wrote: post #20
pontus wrote: post #5

Earlier quoted context omitted.

You entangle two systems but in order to actually complete the teleportation you need to measure one system and then convey the outcome of that measurement to the other party. This information is needed by the second party in order for them to be able to correctly collapse the state of their system into one that is identical to the original system being teleported. The information that the first party must convey to…

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

It clearly makes no practical sense at the moment outside of research.

Re: Sustained, high-fidelity quantum teleportation

#23

Post by [deleted] »

sabellito wrote: post #2

I'm confused, as I'm an enthusiast but definitely no physicist. The article states that quantum information is being teleported via entanglement. However, it was my understanding that one cannot transfer information in such a way as the "information" is only revealed when interacting with the particle. Could someone perhaps clarify what's going on?

[deleted]

Re: Sustained, high-fidelity quantum teleportation

#24

Post by marcosdumay »

junon wrote: post #20
pontus wrote: post #5

Earlier quoted context omitted.

You entangle two systems but in order to actually complete the teleportation you need to measure one system and then convey the outcome of that measurement to the other party. This information is needed by the second party in order for them to be able to correctly collapse the state of their system into one that is identical to the original system being teleported. The information that the first party must convey to…

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

The point is to test physics models.

Re: Sustained, high-fidelity quantum teleportation

#25

Post by kazinator »

pif wrote: post #22
sreejithr wrote: post #3

Does this mean information can be transmitted faster than light speed?

Yes and no. Yes, information can travel with infinite speed. No, cause-effect relationship cannot travel faster than light. https://en.wikipedia.org/wiki/Quantum_nonlocality

> Yes and no.

Could a QM answer be otherwise?

Re: Sustained, high-fidelity quantum teleportation

#26

Post by tgb »

junon wrote: post #20
pontus wrote: post #5

Earlier quoted context omitted.

You entangle two systems but in order to actually complete the teleportation you need to measure one system and then convey the outcome of that measurement to the other party. This information is needed by the second party in order for them to be able to correctly collapse the state of their system into one that is identical to the original system being teleported. The information that the first party must convey to…

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

If you want to transmit 1 quantum bit (qubit), then you need to transmit 2 classical bits. Why is this useful? Because otherwise you have to carry the qubit over by hand. It's really just "quantum ethernet" not "quantum teleportation".

There are actually other uses, too, about error tolerance, allowing you to quality-control some steps of the computation and repeat them if necessary without risking damaging the results of other steps.

Re: Sustained, high-fidelity quantum teleportation

#27

Post by tgb »

boie0025 wrote: post #17
pontus wrote: post #7

Earlier quoted context omitted.

No, while entanglement acts instantaneously across a large distance, there's no way for that "signal" to carry any information. In order to complete the teleportation the two parties must somehow communicate in order to convey an additional piece of information. This communication would be classical and slower than light.

This reveals my severe ignorance about quantum mechanics; but I've always wondered if entanglement could be used to transmit binary data by way of timing and presence or lack of presence of a transmission. So maybe every 1ms is a position, and either something is sent or not.

Quantum teleportation is a process that both sender and receiver have to coordinate. Part of that coordination is that the sender measures 2 classical bits of information on their entangled qubit and transmits those two classical bits to the receiver. Then the receiver uses those two bits to perform certain operations on their half of the entangled qubit pair in such a way that their qubit is now exactly the same as sender's original qubit. As you can see, there's no way to use timing in this, other than the timing of the classical bits being transferred.

Re: Sustained, high-fidelity quantum teleportation

#28

Post by [deleted] »

tgb wrote: post #27
boie0025 wrote: post #17

Earlier quoted context omitted.

This reveals my severe ignorance about quantum mechanics; but I've always wondered if entanglement could be used to transmit binary data by way of timing and presence or lack of presence of a transmission. So maybe every 1ms is a position, and either something is sent or not.

Quantum teleportation is a process that both sender and receiver have to coordinate. Part of that coordination is that the sender measures 2 classical bits of information on their entangled qubit and transmits those two classical bits to the receiver. Then the receiver uses those two bits to perform certain operations on their half of the entangled qubit pair in such a way that their qubit is now exactly the same as…

[deleted]

Re: Sustained, high-fidelity quantum teleportation

#29

Post by abdullahkhalids »

junon wrote: post #20
pontus wrote: post #5

Earlier quoted context omitted.

You entangle two systems but in order to actually complete the teleportation you need to measure one system and then convey the outcome of that measurement to the other party. This information is needed by the second party in order for them to be able to correctly collapse the state of their system into one that is identical to the original system being teleported. The information that the first party must convey to…

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

Physical qubits are much more sensitive to transmission noise than physical bits. If you want to transmit qubits, teleportation allows you to do it with higher fidelity than by physical transmission.

Why do you want to transmit qubits? For various emerging quantum information technologies, each with different potential economic impact.

Re: Sustained, high-fidelity quantum teleportation

#30

Post by roywiggins »

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…

There are game theoretical proofs that show that you can use entanglement to enable better-than-classical performance on games that reward cooperation but disallow actual communication.

https://en.m.wikipedia.org/wiki/Quantum_pseudo-telepathy

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