Can Singlet Spin Pairs Behave Like Bosons?

[anorlunda]

I just studied about the QM of singlet spin pairs. I have additional questions. Neither Wikipedia, nor past threads on this forum seem to address the questions.

1) A pair of electrons forming a singlet pair A. Can the pair be split again into non-entangled electrons? If yes how; just hit it with a photon?

2) Suppose we have two singlet pairs A and B. Can they be brought together without obeying the Fermi exclusion principle?

3) Can we entangle pairs A and B into a quantum system with 4 electrons and 16 spin states?

 

[Avodyne]

1) Yes. Easiest is to measure the spin of one electron (along any axis).

2) The exclusion principle always holds.

3) Assuming we have a universal set of quantum gates with which to manipulate the spins, then we can put them into any state we like, such as the 4-particle GHZ state.

 

[anorlunda]

Thank you Avodyne. Regarding Pauli Exclusion, I was wondering if a singlet pair can behave like a boson, even though the electrons are fermions.

 

[mfb]

Thank you Avodyne. Regarding Pauli Exclusion, I was wondering if a singlet pair can behave like a boson, even though the electrons are fermions.

It can - superconductors or superfluidity of He3 work that way, for example. That does not violate the uncertainty principle - no two fermions have the same state.