Sustained, high-fidelity quantum teleportation • Hacker News Board

Re: Sustained, high-fidelity quantum teleportation

#61

Post by chrisweekly » Fri, Dec 18, 2020, 6:16 PM UTC

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…

Hey yeah I remember reading Penrose's "The Emperor's New Mind" in maybe 1998?, an interesting take on the nature of consciousness... fascinating stuff.

Re: Sustained, high-fidelity quantum teleportation

#62

Post by colechristensen » Fri, Dec 18, 2020, 6:17 PM UTC

pueblito wrote: post #33

abdullahkhalids wrote: post #29

Earlier quoted context omitted.

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.

Does this mean quantum gizmos will ‘teleport’ the data over space instead of using wires? Like, will a quantum processor pull the data in the quantum ram using teleportation?

It means quantum “networking” will be transmitted over classical communications channels.

Re: Sustained, high-fidelity quantum teleportation

#63

Post by lemonspat » Fri, Dec 18, 2020, 6:19 PM UTC

magicalhippo wrote: post #16

lemonspat wrote: post #13

Earlier quoted context omitted.

I think OP is asking, can you entangle, measure, discuss, and then go travel to another galaxy with real time communications? Edit: or can the communication only happen once and then you need to remeasure over classic communication?

> travel to another galaxy with real time communications? As I said, no. How would you relay your measurement results in real-time? Without those measurement results, the receiver would in essence just hear white noise. That's the perplexing part of entanglement. Somehow it feels like information is instantaneously transferred from A to B, yet the information content is somehow zero so can't be used for proper commun…

So you have to measure every time you want to transmit?

Re: Sustained, high-fidelity quantum teleportation

#64

Post by nynx » Fri, Dec 18, 2020, 6:20 PM UTC

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

I remember reading a paper somewhere (can't find it now) on how it should be possible to compress N bits of data into log2(N) qubits. This would be utterly transformative since you could then compress basically any amount of data into just a few qubits (e.g. 1e15 bits would fit in ~50 qubits).

Re: Sustained, high-fidelity quantum teleportation

#65

Post by Snitch-Thursday » Fri, Dec 18, 2020, 6:21 PM UTC

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.

That's exactly what I was thinking! Running far too much into fandon, this holds also for the fictional 'pattern buffer'. It has to examine the original AND communicate that state back to the duplicate quick enough or the 'clone' will be inaccurate, maybe even enough to kill someone a la Star Trek: The Motion Picture.

Re: Sustained, high-fidelity quantum teleportation

#66

Post by drdeca » Fri, Dec 18, 2020, 6:22 PM UTC

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…

Indeed there is a “no cloning theorem”.

Iirc it essentially comes from the fact that time evolution is linear, and a function that sends stateOfIntetest \otimes constantState to stateOfInterest \otimes stateOfInterest for all values of stateOfInterest would be quadratic?

Re: Sustained, high-fidelity quantum teleportation

#67

Post by whatshisface » Fri, Dec 18, 2020, 6:23 PM UTC

nynx wrote: post #64

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

I remember reading a paper somewhere (can't find it now) on how it should be possible to compress N bits of data into log2(N) qubits. This would be utterly transformative since you could then compress basically any amount of data into just a few qubits (e.g. 1e15 bits would fit in ~50 qubits).

You're not going to get that data back out, though. When you measure 50 qbits, you get 50 bits, and you destroy the state irrecoverably.

Re: Sustained, high-fidelity quantum teleportation

#68

Post by nynx » Fri, Dec 18, 2020, 6:24 PM UTC

whatshisface wrote: post #67

nynx wrote: post #64

Earlier quoted context omitted.

I remember reading a paper somewhere (can't find it now) on how it should be possible to compress N bits of data into log2(N) qubits. This would be utterly transformative since you could then compress basically any amount of data into just a few qubits (e.g. 1e15 bits would fit in ~50 qubits).

You're not going to get that data back out, though. When you measure 50 qbits, you get 50 bits, and you destroy the state irrecoverably.

Yeah, I think whether extraction was possible was up in the air. I believe it mentioned that quantum RAM could let you store that data and operate upon it.

Re: Sustained, high-fidelity quantum teleportation

#69

Post by waterhouse » Fri, Dec 18, 2020, 6:25 PM UTC

ajuc wrote: post #56

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.

And classical bits are presumably much easier to transport intact, by several orders of magnitude in terms of cost. Seems the superdense coding would only help if sending qubits were less than 2x as expensive as sending classical bits.

Re: Sustained, high-fidelity quantum teleportation

#70

Post by [deleted] » Fri, Dec 18, 2020, 6:27 PM UTC

nynx wrote: post #68

whatshisface wrote: post #67

Earlier quoted context omitted.

You're not going to get that data back out, though. When you measure 50 qbits, you get 50 bits, and you destroy the state irrecoverably.

Yeah, I think whether extraction was possible was up in the air. I believe it mentioned that quantum RAM could let you store that data and operate upon it.

[deleted]