# B Entanglement and pair-production and annihilation

#### HAYAO

Gold Member
I am confused about entanglement, but I am not a physicist. The concept sounds cool and I want to understand in a way so that it is familiar with what I already know. I want to know if I am interpreting this right:

1) If we have a photon that produces a pair of electron and positron, the electron and the positron is spin entangled after the production. The total spin of the produced pair of particles are the same as the spin of the photon due to spin-conservation.

2) Likewise, if we have a spin-entangled electron and positron with a particular total spin, and is annihilated, it will produce a photon of the same spin.

3) If we have non-entangled electron and positron, then a photon will be produced with a spin of statistical probability depending on the spin of electron and positron before annihilation.

Is any, or all of them wrong?

Also, how are entanglement interpreted in the community of physics? For example, if we have an entangled electron-positron pair, is there some sort of interaction intermediate linking the electron and the positron when one of them is measured for z-projection of the spin so that it automatically determines the z-projection of the spin of the other particle? Or do they have rather agnostic view of how the two particles are entangled ("don't know how but it does" attitude)?

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#### DrChinese

Gold Member
I am confused about entanglement, but I am not a physicist. The concept sounds cool and I want to understand in a way so that it is familiar with what I already know. I want to know if I am interpreting this right:

1) If we have a photon that produces a pair of electron and positron, the electron and the positron is spin entangled after the production. The total spin of the produced pair of particles are the same as the spin of the photon due to spin-conservation.

2) Likewise, if we have a spin-entangled electron and positron with a particular total spin, and is annihilated, it will produce a photon of the same spin.

3) If we have non-entangled electron and positron, then a photon will be produced with a spin of statistical probability depending on the spin of electron and positron before annihilation.

Is any, or all of them wrong?

Also, how are entanglement interpreted in the community of physics? For example, if we have an entangled electron-positron pair, is there some sort of interaction intermediate linking the electron and the positron when one of them is measured for z-projection of the spin so that it automatically determines the z-projection of the spin of the other particle? Or do they have rather agnostic view of how the two particles are entangled ("don't know how but it does" attitude)?
Note: A single photon will not (on its own) produce an electron-positron pair, and vice versa. 2 in and 2 out conserve.

There are many different views ("interpretations") of entanglement, as no one knows the physical mechanism by which components of an entangled system are connected. Agnostic probably being most common interpretation.

#### HAYAO

Gold Member
Note: A single photon will not (on its own) produce an electron-positron pair, and vice versa. 2 in and 2 out conserve.
I assume you are talking about nucleus. Am I right?

There are many different views ("interpretations") of entanglement, as no one knows the physical mechanism by which components of an entangled system are connected. Agnostic probably being most common interpretation.
Thank you, DrChinese. I got it.

"Entanglement and pair-production and annihilation"

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