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/sci/ - Science & Math

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12272134 No.12272134 [Reply] [Original]

Brainlet here, why cant we use Quantum entanglement for FTL communication? If electron on earth has up spin and his entangled pair on Europa has down spin, why cant you just change its spin and use that to send morse code message instantaneously across solar system?

>> No.12272141

Electrons are entangled not because they're linked together magically; they're entangled because of how they were created.

For example, say you have a hypothetical nuclear process that results in two photons being emitted. Every pair of photons released by this process have opposite spins. So you only need to measure one photon to know the spins of both.

>> No.12272148

>If electron on earth has up spin and his entangled pair on Europa has down spin
If you already know the spins then they're determined and not entangled anymore.
>why cant you just change its spin
Because that doesn't somehow flip the other one. It's not magic.

>> No.12272199

>>12272141
But for the point I am making its not really important how particles was created.
> So you only need to measure one photon to know the spins of both
This is what Im getting at, if you can deduce properties of one by knowing that of the other, you could get information across by manipulating those properties (if you wouldnt break entanglement by doing this).
>>12272148
>If you already know the spins then they're determined and not entangled anymore.
Isnt it more that by forcing the spin in particular state you would break the entanglement? Because Im pretty sure that by simply measuring one particle you could get information about the other. I guess my question should if could somehow circumvent this or if its explicitly prohibited by laws of QM

>> No.12272203

>>12272199
Damn I really butchered that last sentence, sorry

>> No.12272209

>>12272141
You would break entanglement by doing that.

Example:
Two photons with opposite spins are created like in my post. They are entangled so if you know the spin of one you can deduce the other. If you take one photon and run it through a polarized filter, it is no longer entangled with the other photon. It is now entangled with the filter, and you can deduce it's spin based on the properties of the filter. You can no longer say the spin of the other photon is the opposite of the polarized filter photon.

>> No.12272211

>create system of entangled photons
>have your buddy measure his one light year away from you, thus collapsing the photon at your location
>measure your photon in its collapsed state
FTL communication? not quite. when you measure your photon, you have no idea whether it has already collapsed or whether you were the one who caused it to collapse. there's no non-destructive way to observe whether or not an entangled particle has been observed already. that's the reason that information can't be conveyed this way.

>> No.12272222

>>12272209
>>12272199
Meant to quote this post

>> No.12272406

>>12272134
Ignore these posts trying to sound smart. Just realise that if you can send information faster-than-light then you can send it back in time. It violates casualty. You could tell yourself next weeks lottery numbers.

>> No.12272759

>>12272406
there is no such thing as faster than light because light doesn't have a speed. what you perceive as the speed of light is just the speed at which the molecules in your body can work. if you take a magic space ship and accelerate until you are at 0.999999999999999% of light speed, light isn't going to be trailing in front of you at a whopping 0.000000671 miles per hour. it's going to be traveling at the speed of light. you've effectively changed nothing but the rate at which the particles in your body are working. you will always see the speed of light as the speed of light, because light is instantaneous, and your mind is bound to the work speed of its composed particles. an object moving at the speed of light requires infinite mass and infinite energy because it's impossible.

when scientists look at terrestrial bodies and see an object moving at 1.1 the speed of light, this is why they know as fact that some external action is being applied to interstellar space, such as the physical expansion of the universe.

>> No.12272934

>>12272134

Changing its spin would break the entanglement.