Can spin be modeled as a spinning vector until "measured" ?

In summary, the projection of the measurement axis onto a spinning vector modeled by a plane would produce correlations of entangled particles in line with what is found by experiment.
  • #1
Jilang
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I was wondering it the projection of the measurement axes onto a spinning vector modeled by a plane would produce correlations of entangled particles in line with what is found by experiment. Does anyone know of any discussions on this subject? Would this lead to stronger correlations than spin modeled as a vector?
 
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  • #2
Spin is sort of like a physical rotation but not in physical space, so no you can't model it as a physical rotation.
 
  • #3
Usually it's a vector right? I meant that the direction of the vector is rotating.
 
  • #4
Jilang said:
I was wondering it the projection of the measurement axes onto a spinning vector modeled by a plane would produce correlations of entangled particles in line with what is found by experiment. Does anyone know of any discussions on this subject? Would this lead to stronger correlations than spin modeled as a vector?
No. What you propose is local hidden-variable theory.
 
  • #5
My favorite article on the interprettion of spin is:
http://people.westminstercollege.edu/faculty/ccline/courses/phys425/AJP_54%286%29_p500.pdf
Ohanian clains that spin is actual angular momentum contained in the momentum density of the wave function, intgrated over space.
 
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  • #6
Gerard Westendorp said:
My favorite article on the interprettion of spin is:
http://people.westminstercollege.edu/faculty/ccline/courses/phys425/AJP_54%286%29_p500.pdf
Ohanian clains that spin is actual angular momentum contained in the momentum density of the wave function, intgrated over space.

Very interesting it feels somewhat weird. How much accepted is Ohanian's interpretation?
 
  • #7
You know for a spin 1/2 particle its state is represented by a vector in C^2 and measurement is modeled as a projection. I am not sure what you are really asking but I think reading a book on quantum computation will help clarify your question. Generally any book on quantum computation will talk about spin 1/2, measurement, entanglement etc.
 
  • #8
I am wondering if it could be modeled as a real vector in three dimensional space spinning very fast in a plane until a magnetic field is introduced, upon which it precesses around the field instead?
 
  • #9
Jilang said:
I am wondering if it could be modeled as a real vector in three dimensional space spinning very fast in a plane until a magnetic field is introduced, upon which it precesses around the field instead?
No, the state of a spin 1/2 particle is a vector in 2d complex vector space rather than a vector in 3d real space.
 
  • #10
Isn't the state just a representation of what we might find on measurement? Isn't QM silent about what is going on until that point?
 
  • #11
Gerard Westendorp said:
My favorite article on the interprettion of spin is:
http://people.westminstercollege.edu/faculty/ccline/courses/phys425/AJP_54%286%29_p500.pdf
Ohanian clains that spin is actual angular momentum contained in the momentum density of the wave function, intgrated over space.

Thanks for this, I've been look for such a thing. This is pretty much what I thought, that it is essentially circular polarization, but I didn't have the math to back it up.

The ultrasimple version is derived from an earthy expression of James Carville. Why does the electron spin? Because it can. If a physical system has a degree of freedom, it will use it if it can.
 
  • #13
I have a problem with the Bloch sphere. The poles represent the z components of spin rather than the spin itself...
 
  • #14
A. Neumaier said:
The two descriptions are mathematically equivalent. See https://en.wikipedia.org/wiki/Bloch_sphere
Yes but SU(2) is not equivalent with SO(3). In the representation of Bloch vector the global phase is missing,
 

1. What is spin and how is it related to the concept of a spinning vector?

Spin is a fundamental property of particles, specifically subatomic particles such as electrons. It refers to the intrinsic angular momentum of a particle, meaning it does not physically spin like a top, but has a quantum mechanical property that behaves like a spinning object. This behavior can be mathematically described using the concept of a spinning vector.

2. How does spin affect the behavior of particles?

Spin plays a crucial role in determining the behavior of particles, especially in the subatomic world. It affects the magnetic properties, stability, and interactions of particles. The spin of a particle also determines its quantum numbers, which are used to identify and classify particles.

3. Can spin be accurately modeled as a spinning vector?

Yes, spin can be modeled as a spinning vector in quantum mechanics. This mathematical model allows us to predict and understand the behavior of particles, particularly in experiments where spin measurements are involved.

4. How is spin measured in experiments?

Spin is typically measured using specialized equipment, such as a Stern-Gerlach apparatus, which uses a magnetic field to separate particles based on their spin states. Other methods include scattering experiments and nuclear magnetic resonance (NMR) techniques.

5. Is spin a classical or quantum concept?

Spin is a quantum concept, meaning it can only be understood within the framework of quantum mechanics. It is a fundamental quantum property that cannot be explained using classical physics principles.

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