Entanglement correlations, singlet spin state

[SpectraCat]

For two electrons to be entangled they have to originate from single place and then move to two different places by unitary evolution. So it's preservation of wave function under unitary evolution that is required as well.

I'm not sure what makes you say that ... electrons in a singlet state are always entangled, right? In fact, in atomic and molecular systems, aren't *all* of the electrons entangled with each other under normal circumstances? This entanglement appears as the exchange integral in electronic structure calculations, for example, which needs to be handled properly to get results that agree with experiment.

I guess what you were saying above applies to macroscopic entanglement experiments
like Aspect etc., but I don't think it is generally correct.

 

[zonde]

I'm not sure what makes you say that ... electrons in a singlet state are always entangled, right? In fact, in atomic and molecular systems, aren't *all* of the electrons entangled with each other under normal circumstances? This entanglement appears as the exchange integral in electronic structure calculations, for example, which needs to be handled properly to get results that agree with experiment.

I guess what you were saying above applies to macroscopic entanglement experiments
like Aspect etc., but I don't think it is generally correct.

I do not quite understand what are your objections.
Entangled particles do not appear from nowhere at two remote places. There has to be some preparation procedure (source) of entangled pair in experiment, right?

 

[msumm21]

zonde: regarding the pauli exclusion principle thing, what i am saying is that i don't think the pauli explusion principle is something you should have to explicitly apply when doing analysis, it should be automatic, a consequence of the more basic rules for constructing wave functions. see, for example p204 of Griffths "Intro to QM, 2nd Ed"

 

[SpectraCat]

I do not quite understand what are your objections.
Entangled particles do not appear from nowhere at two remote places. There has to be some preparation procedure (source) of entangled pair in experiment, right?

Yes, I agree. My only concern was with the apparent generality of your statement:

For two electrons to be entangled they have to originate from single place and then move to two different places by unitary evolution. So it's preservation of wave function under unitary evolution that is required as well.

My point is that your statement applies to macroscopically entangled particles generated in laboratory experiments. Quantum entanglement is a much more general physical phenomenon.