/sci/ - Science & Math

[Anonymous No.12437823]

Brainlet here. If quantum entanglement is faster than light, doesn’t that mean it’s theoretically possible to make FTL communication?

[Anonymous No.12437846]

no

[Anonymous No.12437867]

>>12437823
No, but supposing interaction between entangled pairs were FTL, the answer is still no.

[Anonymous No.12437870]

>>12437867
Why?

[Anonymous No.12437915]

>>12437823
>If quantum entanglement is faster than light
correct

>doesn’t that mean it’s theoretically possible to make FTL communication?
Incorrect. Entanglement has this weird property where the information is invisible to all observers. Look up the quantum eraser experiment. If you try to extract any useful information it will get completely wiped in the measurement process. This problem is fundamental as introducing decoherence is the only possible way to extract information from the system, thus destroying the entanglement, so it can't be circumvented.

[Anonymous No.12437921]

>>12437870
Entanglement doesn't scale. You're assuming that the wavefunction can increase in size to become a macroscopic construct. It's not like that. Shadows travel faster than light due to interleaving. Entanglement has a similar boundary constraint, and has to be built from quantum information up.

[Anonymous No.12437926]

>>12437823
Maybe, you should ask the Chinese, they have mastered quantum communication.

[Anonymous No.12437930]

>>12437823
Entanglement means that particles share correlation in their wave function. It's not a means of transferring info feom one particle to the other.

[Anonymous No.12439045]

why can't you extract information tho?

let's say i'm at one end of the known universe, and my bro at the opposite end. we agree while we were still on earth that we will check the spin state of a pair of entangled particles that we each take with us. if the spin state is 'up' we both put on red hats. if the spin state is 'down' we both put on blue hats. ergo, i know from out of multiple options what color hat my bro is wearing on the other side of the universe. how is this not information? what am i missing?

[Anonymous No.12439050]

>>12437823
It's not, quantum particles have backwards causation, which is to say future events affect the actions of particles before the event has happened.

[Anonymous No.12439066]

>>12439045
Because you have no direct information. Maybe your brother died along the way. It's not communication of any complexity greater than the initial plan.

[Anonymous No.12439070]

>>12439045
it takes time for you to see your friend's hat. in order to verify that the state has collapsed, you have to rely on speed-of-light information transfer, meaning you didn't gain anything

[Anonymous No.12439102]

>>12439045
When two particles are entangled, they have the exact same quantum state, in fact their states are inseparable. They communicate faster than the speed of light, in fact. However, the very act of measuring various properties of one particle, such as spin, collapses the entanglement instantly and the other particle assumes a random state: 50-50 spin up or down, so no information is gained by either party's measurement. If the information on one side is destroyed by scrambling, the other particle assumes a deterministic path with no probabilities involved, even doing so retroactively

[Anonymous No.12439141]

>>12439045
You do know the color of his hat, but you didn't get to choose it for him. That's not sending a message.

[Anonymous No.12439191]

>you and a friend each take half of a large group of entangled particles

>on opposite sides of the universe, you begin observing specific particles in a binary pattern, encoding a message, and causing your friend's entangled particle to simultaneously collapse, transmitting faster than light
checkmate

[Anonymous No.12439199]

>>12439066
ok, i understand this
>>12439070
>it takes time for you to see your friend's hat. in order to verify that the state has collapsed, you have to rely on speed-of-light information transfer
I don't get this one. I thought entanglement was instantaneous. that the exact moment i verify that the spin state is up it will also be up on the other side of the universe?
>>12439102
thank u for a detailed answer, but i may be too much of brainlet to get this. i did not know measuring spin would collapse the entanglement. is there no way of knowing what it was before the measurement then?

[Anonymous No.12439200]

>>12439191
you don't know if something has collapsed without observing it yourself. that's the issue

[Anonymous No.12439209]

>>12439141
ok, its not sending a message, but i got access to info faster than the speed of light would allow. i know he is wearing a red hat because of the state of spin. if he radios me he is wearing a red hat, it would take 26 billion light years for me to get that signal. no?

[Anonymous No.12439234]

>>12439199
I don't think so. In theory you could fire some light at the particle, but the wave properties of the photon dictate that you can't just send one, so the lowest measureable amount of light I believe would still cause collapse.

[Anonymous No.12439240]

>>12437915
I disagree. As a researcher working on quantum entangled particles involved in cryptography, it is possible to find a loop hole around this. Spin states can be ascertained in certain particles and logically inferred on the recipient's end as to what the key and message are.

This can all happen in a cohered state without violating causality concerning transfer of information.

[Anonymous No.12439253]

>>12437921
yes but you are talking about something on the order of a quantum field at this point. You do understand that you are talking about two particles in a quantum field? We're not talking about occlusion and "illusory" objects such as shadows, we're talking about point particles and their wavefunctionality.

Just knowing the particle exists and is sustained in its location without becoming subject to decay, like for example, the center particle in a grid of diamonds, a very stable array, can allow us to achieve stability in FTL communication.

Your boundary constraint are the field constants, like vacuum energy. Which are extremely low in density and would not interfere with FTL propagation of causally inferred information via spin state determination.

[Anonymous No.12439260]

>>12439253
**spin state determination in cohered systems.

I could tell you more about how it works, but then, where's the fun in that? Where's my paycheck?

[Anonymous No.12439265]

>>12439240
Hmm interesting, so does it violate locality though?

[Anonymous No.12439275]

>>12439265
Wait, of course it does, what am I asking?

[Anonymous No.12439284]

>>12437823
I don't see any way to take advantage of entanglement. If you entangle a bunch of particles and take them to opposite sides of the universe, you can measure the up or down spin of one bunch, and know immediatly the corresponding spin of the other bunch on the other side of the universe but the other people don't know what you know and there is no way to tell them. You still need a way to communicate information before you can take advantage of the entanglement.

[Anonymous No.12439285]

The speed limit is on the movement of information. Information can't be communicated via the effects of entanglement.

[Anonymous No.12439289]

>>12439240
>>12439253
All this sounds almost like rube-goldberg, as if the universe is trying to hide something but didn't anticipate some monkey rigging a pulley system in just the right way to find it.

[Anonymous No.12439294]

>>12439045
isn't that the same as writing down a message in an envolope and not opening it until you get to the other side of the universe? that's not ftl information.

[Anonymous No.12439305]

>>12439102
wait what? no

If you measure one particles spin, the state collapses for both particles because their wave functions are entangled. If you measure one with up spin the other will collapse to down.

[KumKum the Kookaburra No.12439307]

>>12437823
Information faster than one can read? What sort of ancient retard are we supporting that still needs to read actual written language?

[KumKum the Kookaburra No.12439310]

>>12439305
Observe. Measure. Record. Compile. Present.

[Anonymous No.12439321]

>>12439305
Are you sure? That's not what I've heard, or that only happens when they're in the same plane orientation.

So at the quantum level information transfer happens faster than light, huh, who knew? So what does that make information? It's not a wave propagating in the vacuum

[Anonymous No.12439348]

>>12437823
>If quantum entanglement is faster than light
It's not.
>it’s theoretically possible to make FTL communication?
Nope.

[Anonymous No.12439353]

>>12439321
>at the quantum level information transfer happens faster than light
No, the entanglement doesn't "travel" or anything. Entanglement is strong correlation. It's "just" nonlocal action, no transfer is happening.

[Anonymous No.12439363]

>>12439353
No, I'm talking about the information transferred across the rube-goldberged entanglements. I get it's a nonlocal action, but you can still transmit information across it, like transmitting encrypted packets across a wire.

[Anonymous No.12439397]

>>12439363
>information transferred across the rube-goldberged entanglements
Can you propose an experiment that shows information is transferred?
>you can still transmit information across it, like transmitting encrypted packets across a wire
Absolutely not.

[KumKum the Kookaburra No.12439596]

Okay, I present all judgement that must be passed onto all observers.

[Anonymous No.12440795]

>>12437823
>>12437921
Wouldn't it be possible to establish communication with entangled particles by changing their location (up, down, left, right etc.) and assign a meaning for each position. since they are entangled, both particles will move, with the manipulator as sender and the non-manipulator as receiver. Now get a hundred particles with a hundred different codings and you got a FTL communications machine. Would probably be hard and costly to stream alien porn on this, but simple text messages should do...

[Anonymous No.12441054]

>>12439348
but entanglement does propagate FTL. the hard part is understanding that that doesn't correlate to information

[Anonymous No.12441332]

>>12441054
Nothing is moving. Entanglement is only strong correlation, and when you separate the involved particles, the entanglement moves with them. No propagation happens when you manipulate one of the states.