Can Singlet Spin Pairs Behave Like Bosons?

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Discussion Overview

The discussion revolves around the quantum mechanics of singlet spin pairs, particularly focusing on their behavior, entanglement, and the implications of the Pauli exclusion principle. Participants explore theoretical questions regarding the manipulation and interaction of these pairs in quantum systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a singlet pair of electrons can be split into non-entangled electrons and suggests that hitting it with a photon might achieve this.
  • Another participant asserts that measuring the spin of one electron can effectively split the singlet pair.
  • There is a query about whether two singlet pairs can be combined without violating the Fermi exclusion principle.
  • A response claims that the exclusion principle always holds, implying that fermions cannot occupy the same quantum state.
  • Participants discuss the possibility of entangling two singlet pairs into a larger quantum system, with one suggesting that a universal set of quantum gates could facilitate this manipulation.
  • One participant raises the idea that singlet pairs might behave like bosons despite the fermionic nature of electrons, referencing phenomena such as superconductivity and superfluidity as examples.
  • Another participant supports this notion, stating that it does not violate the uncertainty principle since no two fermions can occupy the same state.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the Pauli exclusion principle in relation to singlet pairs and their potential bosonic behavior. There is no consensus on the mechanisms for splitting singlet pairs or the interaction of multiple pairs.

Contextual Notes

Participants have not fully resolved the conditions under which singlet pairs can be manipulated or combined, and assumptions regarding the definitions of entanglement and quantum states remain implicit.

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

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