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Sustained, high-fidelity quantum teleportation

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Re: Sustained, high-fidelity quantum teleportation

#121
post #81
post #26

Earlier quoted context omitted.

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 resul…

You still have to carry the qubit over by hand, but you can do it asynchronously to the change

I think that undersells the advantage. You have to carry a qubit over, but it could be done even before know what you will need to send.

Re: Sustained, high-fidelity quantum teleportation

#122

Earlier quoted context omitted.

But that begs the question of how we know that we have produced an entangled pair. Do we not need a metric to use to make sure they are entangled?

The act of measurement on the second particle destroys the entagled state of the pair. That effect can be measured on the first particle's side (which may be far away... on the other side of the galaxy maybe).

But to see/interpret the effect on the first particle, you need to know what the measurement on the second was, and that information needs to be transferred across the galaxy by conventional means.

Honesty quantum mechanics sounds more like a bug in the universe or some quirk we just don’t understand yet.

Re: Sustained, high-fidelity quantum teleportation

#123
post #114

Earlier quoted context omitted.

Thank you for all your comments, very illuminating! Is the following classical analogy flawed? Say you have two pendulums and you set them in motion together so that they swing in perfect synchrony. Then you move the one (still swinging) pendulum to another location without disturbing it. Would it be reasonable to say that the physical pendulums are the “medium” and evolving information about the exact position and v…

It sounds like there's some stuff in your analogy that is similar to the QM situation. I would caution against placing too much emphases on these analogies though since a very important aspect of all of this is not just that the two systems are correlated but rather that they are entangled. There's a classic analogy to this when we talk about entanglement: imagine taking a pair of gloves and mixing them up. Put one i…

The glove explanation is excellent, thank you. I don’t think I’ll ever be able to bend my mind enough to leave Einstein’s spooky action camp. For now I’m just going to start believing that we live in a simulation and that entangled things are just structures that share memory ;)

Re: Sustained, high-fidelity quantum teleportation

#124
You know, something that I think would be interesting in the future would be a detailed comparison between the simplest of radio waves -- and quantum teleportation.

On the one hand, we have the simplest of radio waves -- which moves a little bit of information (depending on how it is encoded, how the radio wave is modulated) over space, and on the other, we have quantum teleportation, which also moves information over space.

On the one hand, the simple radio wave dissipates according to the square of the distance -- the "inverse square law" (https://en.wikipedia.org/wiki/Inverse-square_law), whereas presumably (I do not know), the quantum teleportation does not.

Which leads to a side question -- is there a physical limit to the distance that information can be transported via quantum teleportation?

If not, then there's yet another example of light speed violation, and if so, then maybe the quantum teleportation isn't really quantum teleportation -- but rather some form of radio/wavelike communication at a distance, albeit, one physics has yet to describe...

My point is simply this -- when you have a new fangled, not well understood phenomena (in this case Quantum Teleportation), and you have an old well understood phenomena (for example, radio waves -- but it could be any wave or member of the EM spectrum that conveys information over distance, for example, light), well, when you have two apparently disparate phenomena like that in Physics, you want to understand WHAT AND HOW ARE THEY UNIFIED -- rather than the endless set of attributes that are different between them...

You see, an advanced Physics would be able to express/quantify/explain both radio waves on the low-end of understanding, and every single possible form of quantum teleportation on the high end... IF IT WERE CORRECT...

Observation: What science at this point in time in earth's history needs to do is the following:

1) Construct FTL waves out of Slower-Than-Light waves...

2) Construct Wormholes (Wormhole = Black Hole = Quantum Telportation = Portal, use whatever language you wish!) out of the FTL waves.

Of course, we'll leave #2 for the future.

Goal #1 should be to construct a single, solitary, FTL wave (and be able to detect it over a distance, otherwise what's the point?) from Slower-Than-Light waves.

By default, if you're moving Faster-Than-Light, then the path/space you are moving in has similar characteristics to #2, which, over time, should yield a greater understanding of that phenomenon... (is the space compressed, or the wave expanded, or both?).

In fact, maybe it would make sense to go back to Zeno's paradox of Achilles and the Tortoise: https://en.wikipedia.org/wiki/Zeno%27s_paradoxes#Achilles_an...

That is, if you think about each, each EM wave that exists in space -- must first cross half of that space, but before that, it must cross half of that space, etc., ad infinitum.

So, what happens if an EM wave is made of nothing but space, but space that is twisting, space that is vibrating?

If (and it's a big IF!) that's how EM waves work -- then you already have part of all of the above -- BECAUSE AT THE SMALLEST SCALE IN AN EM WAVE -- SPACE ITSELF IS BEING COMPRESSED AND EXPANDED...

You see, conventional Physics uses words like "Electric Field" and "Magnetic Field" -- rather than such words as "Twist Vector Of Space", "Compression Vector Of Space", "Expansion Vector Of Space", and "Oscillation/Vibration Vector Of Space" (and of course, those are relative to size/wavelength/frequency, etc.... "relative to scale", as I like to say...)

But, I think todays Physics -- would get so much more out of itself -- if we stopped using words like "Electricity" and "Magnetism" -- and instead replaced those with "Something is happening to SPACE here!" (where the something was a more accurate description of what was actually going on!)

But anyway, we need to know/understand/grok the root of all phenomena -- in the simplest of terms -- otherwise Physics will keep inventing a plethora of words and phrases to describe what can be in essence, described by a few simple fundamental understandings in the tersest of ways...

Anyway, feel free to call me a crackpot ... I don't claim to be right -- I only claim that researchers may wish to investigate these subjects further!

Phrased another way "Here be dragons!" -- in programmer parlance!

Re: Sustained, high-fidelity quantum teleportation

#125

Earlier quoted context omitted.

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

No, you have to transmit every time you want to transmit. When measuring one particle of an entangled pair and you get say "spin up", you know immediately that if someone measures the other particle (with the same measurement settings) they'll get "spin down", and vice versa. The chance that you get "spin up" or "spin down" is 50/50 and, as far as we know, cannot be affected or determined in advance. So, on the recei…

That was a very clear explanation, thank you. So all my grand ideas about how quantum communication might work are now sadly dead

Re: Sustained, high-fidelity quantum teleportation

#126
post #114

Earlier quoted context omitted.

It sounds like there's some stuff in your analogy that is similar to the QM situation. I would caution against placing too much emphases on these analogies though since a very important aspect of all of this is not just that the two systems are correlated but rather that they are entangled. There's a classic analogy to this when we talk about entanglement: imagine taking a pair of gloves and mixing them up. Put one i…

The glove explanation is excellent, thank you. I don’t think I’ll ever be able to bend my mind enough to leave Einstein’s spooky action camp. For now I’m just going to start believing that we live in a simulation and that entangled things are just structures that share memory ;)

There is a fairly recent development in theoretical physics called ER=EPR that attempts to clarify entanglement by conjecturing that two entangled particles are equivalent to two particles that have a worm-hole connecting them.

To me, this is a very elegant way of addressing this weird action at a distance.

https://en.wikipedia.org/wiki/ER%3DEPR

Re: Sustained, high-fidelity quantum teleportation

#127
post #20
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 actually in even transferring an arbitrary quantum state from one quantum particle to another, and given an entangled pair existing in advance. Transferring a quantum state from one particle to another isn't an easy or obvious task, because you can't measure it or you would collapse it.

Note that "classical" is just stating that a classical channel is good enough to serve that purpose. A channel that preserves quantum state can of course be used, it's just that that isn't required for this to work.

All classical phenomena are quantum, we just use the word "classical" to describe subsets of quantum phenomena acting qualitatively in ways that are consistent with macroscopic phenomena.

Re: Sustained, high-fidelity quantum teleportation

#128
post #5

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?

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 is a very high quality discussion on QM and explanations from pontus, keep it up!

Re: Sustained, high-fidelity quantum teleportation

#129
post #5

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?

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…

[deleted]

Re: Sustained, high-fidelity quantum teleportation

#130
Can anyone with a better understand than mine compare this experience to the one brought up by a Chinese team in nature in 2017[1]?

I know close to nothing about this domain but these two experiments sounds very similar except for the setup (fiber vs. communication with satellite).

[1] https://www.nature.com/articles/nature23675

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