Stuff about quantum entanglement and the nature of knowledge, split from another thread.

[YNM]

9 hours ago, SpaceMouse said:

a ship capable of jumping via some form of stabilized wormhole.

Someone to fall into a blackhole. XD

But no, it's probably still a no.

4 hours ago, Xd the great said:

In fact, quantum communication, or the above method I have discussed, is currently being developed as a way to prevent hackers intercepting transmission.

You still have to transmit. At light speed.

Only the encryption is "quantum", not the message or the method of transmission.

[Xd the great]

The thing is that quantumn transmission can take place without the limit of light speed.

14 hours ago, Xd the great said:

No delay.

 

By no delay, i mean no delay.

[YNM]

6 hours ago, Xd the great said:

The thing is that quantumn transmission can take place without the limit of light speed.

You misunderstood.

Spoiler

 

I'll be bloody honest, I don't know any piece of shard in the freaking thing to any detail but I know the reason they were interested is due to the possibility of instantaneous key generation and transmission. In other words, it's only the key that's possible to be sent. It has zero meanings - it is meant to be random after all - but that key could be used to both encrypt and decrypt messages.

In fact, the only way you know the entanglement works is by measuring it at both ends then telling each other to see. That "telling" is happening, at most, by light speed.

Never a magic in telling random stuff.

 

And that's the last of off-topics.

Edited June 24, 2018 by YNM

[vger]

On 6/23/2018 at 6:08 AM, Canopus said:

Quantum Entanglement only allows you to remotely alter the state of particles, not teleport anything. And even worse you can‘t use this to transmit information either.

Uh... didn't they just do exactly this just a few months back?

Regardless, of whether or not they can transmit data, I wonder if it's even possible to comprehend how entangled particles are capable of ignoring relativity with their "transmission."

Also, if you want to bake your noodle even more than basic quantum entanglement, check out this variation of the double-slit experiment. https://hackaday.com/2016/09/07/the-quantum-eraser/

Edited June 26, 2018 by vger

[p1t1o]

16 hours ago, vger said:

I wonder if it's even possible to comprehend how entangled particles are capable of ignoring relativity with their "transmission."

I think that there is a working hypothesis that the entangled particles are somehow communicating with other versions of themselves in other realities, a-la "many worlds theorem".

https://en.wikipedia.org/wiki/Elitzur–Vaidman_bomb_tester

[K^2]

On 6/23/2018 at 3:08 AM, Canopus said:

Quantum Entanglement only allows you to remotely alter the state of particles, not teleport anything. And even worse you can‘t use this to transmit information either.

Nitpicking, but thinking of it as changing state of the particle is very confusing. It's better to think of it as changing state of observer. Mathematically, entirely a moot point, which is why both interpretations exist, but when you think about measurement changing state of remote particle, you get into a bad intuitive state where you expect information transmission to be possible. If you think of it as observer's state changing, then it's perfectly clear why no communication takes place.

That said, you can actually use entanglement for teleportation. That's exactly how quantum teleportation works. The catch is that it requires a classical side-channel to operate. So it's real teleportation, and we've done it in a lab, but it's still speed-of-light limited.

 

On the topic of wormholes and warp drives, math says it's possible. Math also says it's going to be very difficult. The crux is that FTL of any kind is equivalent to time-travel in another frame of reference. If you can time travel in some frame of reference, you can construct a closed time-like curve. And all known stable configurations that include closed time-like curves have regions of negative energy density. In other words, to have a stable wormhole or stable warp, you have to have something with negative energy. There's a lot of debate on whether such a thing is even theoretically possible, and whether something like Casimir Effect qualifies. Needless to say, nothing remotely the required magnitudes has ever been observed or even predicted to exist.

But the important keyword above is "stable". There are known unstable configurations that allow for time travel and FTL. Notably, Kerr Metric, which correctly describes space-time near a rotating black hole, when taken to its extreme, produces what is known as naked singularity. A type of ring of finite radius and zero thickness, possessing immense mass and absolutely insane amount of angular momentum, which does not have an event horizon like a conventional black hole, but does have a small region of space around it which allows a particle to exit it before it enters. It is a valid configuration of space-time and does not require anything exotic, like negative energy, but it is known not to be stable. That means we'll have no luck finding one that exists naturally, but it still remains unknown whether such structures can be briefly created artificially. If they can, theoretically, this gives us ability to do all sorts of insane things, and FTL will be just a cherry on top.

Unfortunately, all of this is ridiculously complex computationally. Exact solutions are almost non-existent in GR, and numerical simulations are very expensive. We know all of the equations, but we know almost nothing about possible solutions. And it may take us centuries to run through various possibilities to find something useful. Or we could get lucky, and one of our particle accelerators will produce naked singularities by accident. Stranger things have happened. There just isn't much point in guessing on something that's that far beyond the boundaries of well-understood.

There's also an entire topic of sub-light warp and time-like wormholes. These have no time-travel implications, and so are free of exotic requirements. If there's going to be a way to get to the edge of Solar system in hours instead of decades, I'll take it. FTL may be the holly grail, but simply going light-speed without expending insane amounts of fuel would be fantastic. But even that remains very poorly studied at the moment.

[kerbiloid]

Or instead of bringing the actors there, we should bring the scenery here.
I,e, should stop thinking about the Universe like about a big empty space with worlds far, far away from each other, but think about a player position in an infinte continuous set of locations, and find a way to change the observer's position in the save file. 
Not move his body, but choose  a body similar to his, being in a desired state (including the desired scenery), as in multiverse version nothing is unique, so you have a technically infinite number of states including yous and planets-where-you-are.

So, the solution can be not in physics itself, but in researching what the mind is, and where/how it's placed.
(As any brain is just a cloud of particles, which you shake many times per day).
The "observer" physical term is still not defined properly if speak about any type of entanglement.
Also, "how many bits of information are there in "E=mc2" formula ?"
And what is exact speed value of observer's transition from "I don't know" to "I know" states?

(Caution! Do not try this at home. A specially trained metagalactic police (wearing white clothes) tries to return space-time travellers back to home in rooms with soft light and walls).

Edited June 27, 2018 by kerbiloid

[vger]

22 hours ago, p1t1o said:

I think that there is a working hypothesis that the entangled particles are somehow communicating with other versions of themselves in other realities, a-la "many worlds theorem".

https://en.wikipedia.org/wiki/Elitzur–Vaidman_bomb_tester

Good explanation for why the communication aspect doesn't actually work as we wish it would. But also, dagnabbit, my google-fu is failing me at the moment. Anyone remember an experiment in the past year or so where someone actually figured out a way to observe photons in the double-slit experiment without altering their behavior? My gut tells me there's a way around the quantum-entanglement communication problem. Or at least, I have much higher hopes we'll be able to do this in the near future compared to warp drive.

[p1t1o]

14 minutes ago, vger said:

Good explanation for why the communication aspect doesn't actually work as we wish it would. But also, dagnabbit, my google-fu is failing me at the moment. Anyone remember an experiment in the past year or so where someone actually figured out a way to observe photons in the double-slit experiment without altering their behavior? My gut tells me there's a way around the quantum-entanglement communication problem. Or at least, I have much higher hopes we'll be able to do this in the near future compared to warp drive.

Im not saying any of those things are impossible, but quantum physics cares nothing about your gut, and often does things that are wholly counter-intuitive. (Which, ironically, would include FTL stuff, but it doesnt help in wondering how likely it is)

Ponder this - lets say you receive a message from the future, how do you know its from the future? 

Edited June 27, 2018 by p1t1o

[vger]

1 minute ago, p1t1o said:

Im not saying any of those things are impossible, but quantum physics cares nothing about your gut, and often does things that are wholly counter-intuitive.

Ponder this - lets say you receive a message from the future, how do you know its from the future? 

A very good question, especially when experiments have shown that measuring a particle can even retroactively alter its state, BEFORE you measured it. Taking that into account though, I'm completely baffled how quantum computing would ever work since it seems to have to be governed by the same principle. How are qbits of any use if read/write can't be done accurately?

[kerbiloid]

Spoiler

14 minutes ago, p1t1o said:

lets say you receive a message from the future, how do you know its from the future? 

All good people have defeated all bad people.

 

[vger]

@kerbiloid Dang, that was profound. You just solved a riddle that nobody intentionally made.

[kerbiloid]

4 minutes ago, vger said:

@kerbiloid Dang, that was profound. You just solved a riddle that nobody intentionally made.

Now you know how a letter from future looks. An answer before a question.

Btw, somebody should leave this here.
https://vinepair.com/articles/stephen-hawking-time-travel-party/

Edited June 27, 2018 by kerbiloid

[p1t1o]

45 minutes ago, kerbiloid said:

  Hide contents

All good people have defeated all bad people.

 

lol, I'd see that as confirmation that the message was fake...

[K^2]

10 hours ago, vger said:

Good explanation for why the communication aspect doesn't actually work as we wish it would. But also, dagnabbit, my google-fu is failing me at the moment. Anyone remember an experiment in the past year or so where someone actually figured out a way to observe photons in the double-slit experiment without altering their behavior? My gut tells me there's a way around the quantum-entanglement communication problem. Or at least, I have much higher hopes we'll be able to do this in the near future compared to warp drive.

The No-Communication Theorem is a theorem. That's why we call it that. That means that it's not something we don't think can be done. Or that we have strong evidence that it can't be done. It's that it absolutely cannot be done, with an actual mathematical proof. Entanglement does not work this way. It's possible that there is no such thing as entanglement, and we are seeing a completely unrelated phenomenon which we have not been able to distinguish from entanglement experimentally so far, but one that works by an entirely unknown mechanism which allows for causality violations, because the whole of Quantum Mechanics is absolutely wrong. But a) don't hold your breath for it, and b) even if it turns out to be the case, it means that absolutely all of physics is wrong, and anything is just a guess.

Entanglement, though, cannot be used for communication. That is a mathematical fact.

That doesn't burry the entire concept of FTL; we have several known loopholes in theory that allow for completely different ways to send signals FTL, and there can be other, undiscovered mechanisms for superluminal communication. But it's not entanglement. I can't stress it enough.

[kerbiloid]

1 hour ago, K^2 said:

it means that absolutely all of physics is wrong

Not wrong but its applicability is limited with particular conditions.
But this is how science works.

1 hour ago, K^2 said:

and anything is just a guess.

And this is how science works. A natural selection of guesses by observed facts. Nobody has a book with answers.

If tomorrow we'll discover that we live in a computer game, and all physical laws are just coded, while physical constants are taken from a config file, this will mean just that the current scientific knowledge describes the game situations we have observed, not that it's wrong.

2 hours ago, K^2 said:

Entanglement, though, cannot be used for communication. That is a mathematical fact.

That's an assumption based on an axiom "we can't change the past as this would cause eventual paradoxes" and on unclear nature of a time dimension.
But this breaks a more general principle: reversibility of physical laws.
So, if we can distinguish the past and the future, we are just studying a particular case. Just not enough current knowledge.

[YNM]

26 minutes ago, kerbiloid said:

That's an assumption based on an axiom "we can't change the past as this would cause eventual paradoxes" and on unclear nature of a time dimension.

No.

It is purely based on the fact that you can't make information upon randomness.

Hence it's potent as a random key distributor.

[YNM]

13 minutes ago, kerbiloid said:

Another assumption...

No.

There's a reason why obscure gags makes no-one laugh.

[kerbiloid]

12 minutes ago, YNM said:

No.

Even Landau wasn't able to give a clear answer, how the 2nd law can not contradict the reversibility principle, when was asked.
 

12 minutes ago, YNM said:

There's a reason why obscure gags makes no-one laugh.

Ok, let's bring some gags.

Was the Universe after Big Bang highly structurized or chaotic? 
Was it a low-entropy crystal or a high-entropy chaotic cloud of plasma?

What is more structurized: Solar System or protosolar gas cloud?

Edited June 28, 2018 by kerbiloid

[YNM]

1 hour ago, kerbiloid said:

reversibility principle

What reversibility ? You mean symmetry ?

If you mean symmetry, it may as well be dead.

 

Edited June 28, 2018 by YNM

[kerbiloid]

1 hour ago, YNM said:

What reversibility ? You mean parity ?

?
I mean "reversibility of physical laws". 
An equation must work with both t and -t.
When you have a hamiltonian mechanics equation, it works in both directions. It doesn't know about entropy or so.
Entropy, thermodynamics and other terms are just a generalisation of most probable system dynamics, nothing more. On low level you just have an indestructible close set of energies and impulses interacting in a clear way, being described in time-reversible equations.

Yes, probably "parity" here is what I mean as "reversibility", from "reversible".
I can't' find a correct English translation for "обратимость", and tried to avoid an ambiguity with other "parities" known in physics.

So, what this video proves?

Spoiler

Btw about video:
00:23.
Red cross and sound alarm are a dirty trick, which do not the video better, authors axiomatically force to follow them.
The balls can get into one corner at once, just probability is low.

02:05
The whole sentence starts with: "One way out of the difficulty is to assume that parity is ...".
This isn't included into a popup box.
But of course another popup box includes "parity conservation is so far on;y a hypotheis".

So, another obviously intentional manipulation. Hide one hypothesis "assume", but highlight another one's "so far only an extrapolated hypothesis".
What is "parity conservation"? Parity is not an amount of something, it's like saying about "conservation of plus and minus".
Parity is not at all "extrapolated", it's just a sign of value in equation. By the same reason, it's not a "hypothesis", that's like saying "a hypothesis that a square root may have two values with opposite sign".
What is this ad hominem "so far only a" in a scientific work?
"Unsupported by experimental evidence"? Really? The wholel orbital mechanics and astronomy is based on this "extrapolated hypothesis", btw.

02:30
Can't see how the experiment with cobalt atoms tells anything about the parity (in sense of "time-reversibility") .
1. The system is not closed. The atoms emit energy which gets lost, they are effected by magnetic field from external sources (consisting of other particles).
2. Where is _time parity here? Where is the reversed experiment: atoms get the electrons and photons from the same directions, and the system doesn't get into initial state?

"It's crazy", "this is exactly what", "This destroys basic assumptions of theoretical physics"
Really?
The only thing it really breaks are conservation laws. And this mostly tells about the experiment consistency, not about conservation laws.

All this experiment has shown, is that a current physical model can be insufficient in particular cases. (Like somebody doesn't know that.)

When physics contradict mathematics, then just the physics is incomplete.
Hamiltonian mechanics (the basics of theoretical physics) is a pure mathematics, it can't be wrong.

Edited June 28, 2018 by kerbiloid

[K^2]

2 hours ago, kerbiloid said:

Not wrong but its applicability is limited with particular conditions.
But this is how science works.

You are confusing ad-hoc parameters with core assumptions of the model. This isn't like gravity being wrong in Newtonian physics, and still acting as a good approximation. This is like if conservation of momentum in Netwonian physics was wrong. That is a total deal-breaker. Superposition is one of the core assumption of field theory, and leads directly to concept of entanglement. And absolutely all of modern physics is built on top of field theory. From high-energy physics to cosmology. Entanglement allowing for communication violates the most fundamental assumptions. Throwing these way means throwing away the entire theory. It wouldn't make it just imprecise, but absolutely wrong at its root. In other words, you can't expect entanglement to produce communication, and at the same time being able to use modern physics to predict anything. To be that wrong on entanglement, it has to be wrong on everything. That's also why communication via entanglement is a statistical impossibility, but that's a separate talk.

2 hours ago, kerbiloid said:

That's an assumption based on an axiom "we can't change the past as this would cause eventual paradoxes" and on unclear nature of a time dimension.

No. If you are going to argue this point, I suggest you first learn what entanglement is from perspective of relevant mathematics, and look up derivation of no-communication. It has nothing to do with paradoxes. Entanglement works exactly the same way even in conditions where time travel is a thing, such as T⁴ space-time as the most trivial example. You have to be super-careful with these, but you can absolutely deal with time travel in QM setting without any serious issues. More importantly, this is not an assumption based on an axiom. It is a theorem. Which means, if there is superposition, there is no communication via entanglement. If you can find communication via entanglement, all of the physics is wrong - see above. That's how logic and math work. Science is what we build on top of these concepts, and you don't get to apply scientific method to mathematical formulae. It only flows the other way.

 

Quote

I can't' find a correct English translation for "обратимость", and tried to avoid an ambiguity with other "parities" known in physics.

No, that video talks specifically about time not being reversible. You're actually 100% wrong about it. If you flip t to -t, some left-handed particles start working like right-handed particles instead. Now, if you flip charge, parity, AND reverse time, then you're good. So we still have a symmetry to work with, it just happened to be a bit more complex than we thought. That's another example, by the way. Fact that we were off on the nature of symmetry, is the ad-hoc part. Fact that symmetry is there is fundamental to theory. If we don't have SOME form of TCP equivalent, we have to throw all of our physics away. But if it's merely TCPXYZW sort of symmetry, we can keep going. THAT is how science works. And particle physics is probably where it is illustrated the best.

Edited June 28, 2018 by K^2

[kerbiloid]

2 minutes ago, K^2 said:

assumptions

That's a good word.
Light speed limit is btw just an assumption, postulated to define the boundaries where the relativistic theory is applicable.
Just these assumptions work fine in the very limited set of physical conditions available in nowadays experiments.

5 minutes ago, K^2 said:

No. If you are going to argue this point, I suggest you first learn what entanglement is from perspective of relevant mathematics, and look up derivation of no-communication. It has nothing to do with paradoxes. Entanglement works exactly the same way even in conditions where time travel is a thing, such as T⁴ space-time as the most trivial example.

Nice. What if an entangled particle disappears in a black hole?

[K^2]

Just now, kerbiloid said:

Light speed limit is btw just an assumption

There is no such assumption in modern physics. In fact, we know it not to be true. Universe expands faster than light. FTL travel is impractical, but all you have to do is travel fast enough for long enough, and you WILL be going FTL relative to Earth. Care to try again?

Just now, kerbiloid said:

Nice. What if an entangled particle disappears in a black hole?

The state of the black hole is now entangled to the original system. Whether that matters depends on which state it was. If, like in most experiments, you're entangling angular momentum, then angular momentum of the black hole itself is now in a super-position entangled with the state of the test particle. This isn't Voodoo or some dark secrets. It's not even rocket science. It's literally first year course in QM.

[kerbiloid]

20 minutes ago, K^2 said:

some left-handed particles start working like right-handed particles instead.

In the model where there are left- and right- handed particles, which is an assumption based on interpretation of experimentally observed facts.

9 minutes ago, K^2 said:

Universe expands faster than light.

An assumption based on mathematically described interpretation of observable facts.

No experiments can prove or disprove this, because they are just experiments.
Experiments are to describe what we roughly can observe and make assumptions to be used in practice.
No experiment can be enough abstract, it's always dirty and incomplete.

Edited June 28, 2018 by kerbiloid