Undergrad Curious about an idea of a modified polariser to send signals with QE

[tade]

But within relativistic microcausal QFT by construction there are no spooky actions at a distance, only long-ranged correlations between parts of an entangled quantum system.

though i think there's the question of how they get correlated at a long-range within a very short duration, for example the lower bound of the "entanglement speed" being 10,000c

 

[vanhees71]

They get correlated through the preparation procedure. E.g., to have two photons in an entangled state you can use parametric downconversion and select only entangled pairs, i.e., these two photons moving in different directions are all the time entangled until they are detected, and the detection events can be as far as you like. As long there's no interaction of the photons on their way to the detector you'll just measure the strong correlations (of their polarization) which are there all the time since the photons have been created.

 

[tade]

these two photons moving in different directions are all the time entangled until they are detected, and the detection events can be as far as you like. As long there's no interaction of the photons on their way to the detector you'll just measure the strong correlations (of their polarization) which are there all the time since the photons have been created.

hmm that does sound like spooky action at a distance lol

 

[vanhees71]

Why should this be spooky action at a distance? The photons have been created by a local action, e.g., when using parametric down-conversion the interaction of a laser beam with a BBO.

 

[tade]

Why should this be spooky action at a distance? The photons have been created by a local action, e.g., when using parametric down-conversion the interaction of a laser beam with a BBO.

as in, hmm, maybe you can elaborate on the part about the photons being all the time entangled

 

[vanhees71]

You create two photons in an entangled state, like
$$|\Psi \rangle=\frac{1}{\sqrt{2}} [\hat{a}^{\dagger}(\vec{p}_1,h=1) \hat{a}^{\dagger}(\vec{p}_2,h=-1) -\hat{a}^{\dagger}(\vec{p}_1,h=-1) \hat{a}^{\dagger}(\vec{p}_2,h=1)]|\Omega \rangle.$$
If neither of the photons interact with anything, they stay in this state forever.

 

[tade]

You create two photons in an entangled state, like
$$|\Psi \rangle=\frac{1}{\sqrt{2}} [\hat{a}^{\dagger}(\vec{p}_1,h=1) \hat{a}^{\dagger}(\vec{p}_2,h=-1) -\hat{a}^{\dagger}(\vec{p}_1,h=-1) \hat{a}^{\dagger}(\vec{p}_2,h=1)]|\Omega \rangle.$$
If neither of the photons interact with anything, they stay in this state forever.

oh i see, and i was thinking that if both are measured in quick succession, as both are entangled, there could be the spooky action at a distance

 

[PeterDonis]

there could be the spooky action at a distance

This phrase is meaningless unless you define what, in the actual math, it corresponds to. So far we have had two possible definitions: violation of the Bell inequalities, and entanglement of the two photons. Neither of these seems to be what you mean, but you seem unable to give any other definition. If that is the case, there is probably no point in continuing this thread, since the actual physics has already been discussed in some detail.

 

[tade]

This phrase is meaningless unless you define what, in the actual math, it corresponds to. So far we have had two possible definitions: violation of the Bell inequalities, and entanglement of the two photons. Neither of these seems to be what you mean, but you seem unable to give any other definition. If that is the case, there is probably no point in continuing this thread, since the actual physics has already been discussed in some detail.

maybe another notion would be one photon sending info to the other photon instantaneously across a great distance

and i would also like to ask about taking a look at any literature on the the maths and mechanics of the situation at the moment when the wave encounters the molecules of the polariser, the interaction of the target particle with the polariser molecules, like the photon-polariser interactions at the quantum-molecular level, or also the maths of the transition when and as the wavefunction is collapsing as it encounters and interacts with the molecules of the polariser

though yeah i think some of the parts might not have existent literature as of yet

 

[PeterDonis]

maybe another notion would be one photon sending info to the other photon instantaneously across a great distance

I said something in the actual math. I did not say whatever your imagination can dream up.

i would also like to ask about taking a look at any literature on the the maths and mechanics of the situation at the moment when the wave encounters the molecules of the polariser, the interaction of the target particle with the polariser molecules, like the photon-polariser interactions at the quantum-molecular level, or also the maths of the transition when and as the wavefunction is collapsing as it encounters and interacts with the molecules of the polariser

This is well beyond the scope of a single PF thread. Basically you are asking for a complete course in quantum measurement techniques and solid state physics.

The thread topic has been sufficiently discussed and personal speculation is off limits here at PF. Thread closed.