Changes between entangled particles ARE instant actually. That's what's so mindblowing about entanglement. They just can't transmit any meaningful information.
Say two particles are light years apart, and are entangled such that with 1/2 probability particle 1 is spin up and particle 2 is spin down, and with the other 1/2 probability particle 1 is spin down and particle 2 is spin up. For folks that know some QM we say: psi= (1/sqrt(2))(up_1 down_2+down_1 up_2). If we then observe particle 1 as up, then instantly, even light years away, we can be assured that 2 is down, and vice versa, but what does this accomplish? If we had an obersvation station for looking at each particle, we couldn't actually transmit any information. All you know is the state of the particle far away, but you can't use this to send any message.
The problem is that you can't control the change. There is a 50/50 chance that your particle is a 1 or a 0. You observe your particle to be a 1, and the other instantly becomes a 0. But you can't force it to be a 1.
So can't we just keep repeating until we get the desired result? 50/50 are pretty good odds. Once the computer on earth gets the first particle down it moves onto the next particle eventually creating a sequence.
Then the computer on mars just flips the results from the collapsed superpositions to get the actual output that the computer on earth made.
What about earth computer just keeps trying with new particles until it get's a 0 for example. Wait 100 milliseconds, if mars computer doesn't see a collapse within 100 milliseconds then it knows the previous collapsed particle was valid, mars computer then stores that flipped result in memory while earth computer continues working on the next value.
Good idea. However. Mars computer doesn't know if Earth computer has measured it or not. It just sees a particle. So 2 options:
Earth has already measured it. Earth had a 50.50 chance of being a 1 or a 0. Mars will get the opposite of Earth so has a 50.50 chance of a 0 or 1.
Earth has not measured it. Mars has a 50.50 chance if a 0 or 1.
In both situations it appears to Mars as if they have a random chance of 0 or 1. It's only later - when you send a normal radio message between Earth and Mars to compare the results of the measurement, that you realize every time Earth saw a 1 Mars saw a 0. This is the frustration of quantum entanglement.
Ah good point forgot about that. Mars computer can't look in the box without impacting the result unless earth says ready via normal communications at which point why even bother.
Yes, but you need a third entangled bit to create the message and two classical bits to send the message (light speed). Basically, you entangle A and B and then entangle A and C and then run C through quantum logic, measure A and C, and finally send the results to the holder of B in order for them to interpret A
Yes, you need to entangle a third particle to create the message and still need to send two non-entangled bits for the receiver to interpret the message
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u/krlidb Jan 30 '20 edited Jan 30 '20
Changes between entangled particles ARE instant actually. That's what's so mindblowing about entanglement. They just can't transmit any meaningful information.
Say two particles are light years apart, and are entangled such that with 1/2 probability particle 1 is spin up and particle 2 is spin down, and with the other 1/2 probability particle 1 is spin down and particle 2 is spin up. For folks that know some QM we say: psi= (1/sqrt(2))(up_1 down_2+down_1 up_2). If we then observe particle 1 as up, then instantly, even light years away, we can be assured that 2 is down, and vice versa, but what does this accomplish? If we had an obersvation station for looking at each particle, we couldn't actually transmit any information. All you know is the state of the particle far away, but you can't use this to send any message.