How does Quantum Entanglement not allow FTL communication? I can't understand this

Measuring doesn't alter the state though. Lets say I give you two cards face down, and tell you one of them has the letter A on it, the other has the letter B. You then turn one card over and find it has A on it. You then automatically know the other card says B. There's no information being sent anywhere, it's just logic.

Then the Schrödinger equation is god. (And linearity)

You measure what you got the first time as the entangled state has effectively been destroyed with the destruction of the superposition state.

Measuring does alter the state, but in a way where your statement is generally correct if both parties perform the same measurement [say measuring the z-projection of the spin of some particle]. But the test of entanglement involves the parties carrying out random, uncorrelated [though non-commuting, like one may measure the z-projection of the spin and the other the x-projection of the spin] measurements and looking for correlations in their results.

>You measure what you got the first time as the entangled state has effectively been destroyed with the destruction of the superposition state.

So would the two particles have to be "re-entangled" again before another measurement could be made?

It's a shame they can't be re-entangled at a great distance. You could keep re-entangling and measuring at high speeds until you got the measurement you wanted, then at the end of a short pre-defined period (once every second or whatever) the "receiving" end reads the measurement.

please kindly stfu

In your example, measuring does alter the state, it goes from a superposition of two opposite states, call them A-B and B-A, to one state. Superpositions are real, you can see them in the interference pattern in the double slit experiment.

In the many worlds interpretation, all quantum event outcome possibilities can exist overlapped in our deterministic, decohered world, so long as we have no causal interaction or information about their state.

Your statement is sort of right, when you know A you know B instantly, the mechanism is that you basically just eliminate one state by eliminating the ambiguity through measurement. One state pops out of the superposition. The other remains split off into the Level 3 Multiverse.

Say I have two coins, magically linked, and when you flip one coin to heads, the other turns tails. However, you can't determine if either is heads or tails until you catch them. Until then, these magical coins are constantly spinning and the outcome unknown. You can't decide to pin the coin into a particular state, the result is always totally random and outside your ability to control. Further, you can never tell if the either magic coin has been flipped, you can only read the random result.

So I give you one, and you magically teleport to a galaxy far, far away, while I have the other.

So we decide, adjusting for relativity and the distance between us, that I'll catch my coin at a predetermined synchronized time, at which point you'll catch yours, and see the result.

But... The as the result is random and you can't even confirm if or when I've flipped the coin, we've no way to communicate anything this way.

While it's entirely possible to violate the speed of light in a number of ephemeral ways, it's impossible to transmit information at faster than the speed of light (which is, really, just the speed of information propagation) lest you start warping or bypassing the distance somehow. These magic coins, thus, do not violate this law, and is the same fashion in which quantum entanglement respects it.

But you could send sealed messages all over the world, and just have everyone open theirs at UTC midnight. (Okay, still not a violation, assuming the boxes with the information arrive via UPS Air - but fun at geek parties.)

yeah, but you can exploit this

No-communication theorem say it can never be used to transmit information.

you're wasting your education

>How does Quantum Entanglement not allow FTL communication? I can't understand this.
Because there's no causality.
Measuring a particle's spin doesn't create the spin itself, and therefore doesn't create the spin of the other particle.
Causality doesn't (and can't) exceed c.
Therefore, whatever's happening does NOT involve one particle changing the other at a distance.

The same way a projection or a shadow can "move" faster than light, while no information travels faster than that if you consider everything involved

The true random nature of a particles wave function means that we can't actually transmit any information that we don't already know. The rest is non-deterministic and no information can actually be extracted.

>Veeky Forums physics

wew lad

>Therefore, whatever's happening does NOT involve one particle changing the other at a distance.
Unless there are non-local hidden variables (see Bohmian mechanics/deBrogglie wave guides).

that's a pretty weak counter since you're already assuming non-locality. Just assume non-locality and this isn't even an issue

I do not really think non-local hidden variables hold much water (good luck extending Bohmian mechanics to QFT), but they are a valid solution to the violation of the Bell inequalities that does away with quantum weirdness and entanglement.

I was reading about nonlocal entanglement a while back, from what I understood it states that some particles can have a perfect clone of themselves (with all the same properties) somewhere in the universe. Doesn't it mean we could analyze the state of a far away particle (e.g. a photon) by observing a local clone? for example, if a hundred of photons who have their clone under observation hit a meteor, could that be used to obtain informations about said meteor?

What's that? Science doesn't understand jack shit about reality?

You don't say!

Enjoy your Science Delusion!

my BBC gets in the way because its 2 big.

All photons are identical. As are all electrons, quarks, neutrinos, etc. Extending upwards, all hydrogen atoms of the same isotope are identical. I cannot tell anything about a different hydrogen atom by observing one hydrogen atom unless they are entangled in a specific way and the observation really just tells me what state the hydrogen atom was in if it happens to have collided with something big (like a meteor) because that is mechanically the same as measuring the state and destroys the superposition which allowed for entanglement.

Nothing is identical. Nothing. Not even electrons, protons, quarks, nothing.

You can actually manipulate the superposition to make a certain spin for example very likely and then do some error correction. It would require syncing or something so your data rate would be limited to some external clock signal by radio for example. Also you must keep the measurement orientation parallel between the entangled particles somehow, which is hard to do when your spaceship is a gorillian light years away. Then another issue is that every entangled particle you take with you is one time use.

Yes they are, they are just excitations in their field and there is only one field for a particle after all.

But that's wrong.

Yeah but you can only re-entangle them by bringing them back together which destroys any possibility of FTL information transfer.

How do you tell the difference between the two electrons in a Helium atom?

>electron particle = a
>Photon particle = b

so forth and so forth.

You haven't explained anything

Thats how it would work as one example.

OR

Use quantum dots and a super conducting wire to entangle photons, then tune the quantum dot to relay the message.

You're just putting words together.

Tell me how you would reliably transmit a one bit message using this. 0 or 1, up or down, whatever.

As a general rule of thumb, if you don't understand something, Veeky Forums is not the place to come for answers.

They are as unique as everything else in the universe; every grain of sand, every snowflake, every fingerprint.

By knowing Who made them, and how He creates things. There's no copy pasta in the universe. No matter how good your microscope is, or how powerful your telescope is, you'll never max out His designs.

Nah, those are just unique because they're made of the identical things in unique ways.

Others have explained this well enough. Think of quantum entanglement like sending two letters on opposite sides of the universe. If you then open one, you immediately know what both letters say. But because nobody could have written anything on it, the contents will be random, if same, on both letters.

But the inability to transfer information is not entirely correct however. Basically, you CAN use quantum entanglement to synchronize random, but shared information.

Let's say you send out 10 warships into space, with distances of several light years inbetween each warship. You agree that on the same standard time after 2 years, they will check the spins of their entangled particles. If the particles have an up spin, the ships keep going. If they have a down spin, they return to base.

Suddenly, you have a synchronized decision over vast distances that shouldn't have been communicated. Except of course, the decision was random.

In a similar vein of thought, you could entangle several groups of particles and send them out every which way, while agreeing upon a code for instance. If 99 particle groups measure up and 1 down, it will produce the letter A, if 84 up and 16 down, K, etc. There could be hundreds to different tactics, each specific to each ship, but since they would always receive the same letter, the tactics could be predetermined in a way that eventually each ship is fulfilling a very specific role towards a common goal.

This makes no sense for current warfare for instance. But it does have very real applications for cryptography, and I imagine if space battles ever become a reality, employing the ability to make instantaneous synchronized decisions, even if picked from a random table of possibilities, would have a definite role in relativistic warfare for instance.

What are you fucking retarded?
when a super conductor is active near a quantum dot, it becomes entangled and takes some of the properties, such as acting slightly like a liquid/solid based on what frequency the quantum dot is at the time. Take those photons, put them somewhere else, and proceed to tune the quantum dot. Derive message from it's frequency change.

You'll never, ever, ever find two things identical in this universe.

Never.

you can set up FTL communication with shadows.

youtube.com/watch?v=JTvcpdfGUtQ

This would be quite a revolution in physics, seeing how the entirety of statistical mechanics and quantum mechanics are based on identical particles which result in physical phenomena that are experimentally confirmed to wildly-accurate precision. Some of the most-accurate theoretical predictions in the history of mankind are due to phenomena specific to the formalism of identical particles.

But I'm sure you have a very good reason to believe each and every particle is distinct beyond your gut feeling. If you enumerated these differences so the rest of us could benefit from your insight, you're guaranteed a Nobel prize.

You're on to something. In game theory we often have the best solution as a mixed solution, many games are played perfectly at random, for example: rock paper scissors.

Whats wrong with that interpretation?

how so?

Anything you get from that will be random though, there's no way of using that to transmit a defined message.

>How does Quantum Entanglement not allow FTL communication? I can't understand this.

Because mathematicians don't understand light cones.

Fucking this. Sad to see how uncreative people are about this

How ?

You can exploit this but not to send information, look up Quantum Key Distribution.

It's pretty creative.

see
for example.

Also, you can have 2 people gather knowledge about something, no matter how far apart they are. come on

Yeah but you still can't have person A send well defined information to person B faster than light

>brainlet thinks our current knowledge is advanced