# Questions tagged [quantum-spin]

Fundamental characteristic property of particles which together with orbital angular momentum acts as the generator of rotations and which doesn't have a classical equivalent but is sometimes compared to and contrasted with classical intrinsic angular momentum.

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### Complex rabi frequency

I am learning quantum optics. In the book written by Scully includes complex rabi frequency, when dealing with $\Delta$ level configuration, the Hamiltonian including laser-atom interacting concludes ...
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### Which book (or article) has detailed calculation for Quantum Heisenberg Model for three or four spins?

A I need to write a program to calculate Quantum Heisenberg Model for any number of spins (with or without external magnetic field). Each spin is spin 1/2. I know how to do this calculation for two ...
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### What is the value of the inner product $_x\langle+|-\rangle$?

I know that $\left|_x\langle+|-\rangle\right|^2 = 1/2$, so is it just as simple as taking the square root of $1/2$? Thanks.
1answer
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### Why is it that the Callan-Gross relation predicts that quark has spin 1/2?

I'm studying deep inelastic scattering, and currently at the part where they say the Callan-Gross relation: $$F_1 (x) = \frac{1}{2x} F_x (x)$$ where $F_1$ and $F_2$ are the dimensionless structure ...
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### What is the 4-spin vector of a photon?

The photon, being a vector boson has 2 spin states, $\pm 1$. In relativity, we can determine the four-spin vector $s^{\mu}$ of a particle (see e.g. Costa et al. 2017). What would $s^{\mu}$ be for a ...
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### Stern-Gerlach experiment interpretation [on hold]

It seems to me there is a problem with the usual interpretation of the Stern-Gerlach experiment. Sending a magnetic dipole on a path through a magnetic field would, on classical assumptions, affect ...
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### Direct measurement of $\mathbf S^2$

For concreteness, consider two spin-1/2 particles with spin vectors $\mathbf S_i=(S_i^x,S_i^y, S_i^z)$. The total Hilbertspace is four-dimensional, and as a basis we can take the (simultaneous) ...
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### Does electron affinity decrease with charging?

Lets consider two materials A having higher electron affinity than B while both are not too far off. If they are both insulators and A accumulate charges due to triboelectric effect. Than after a ...
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### Quantum Mechanical Treatment of the Spin Echo

I'm trying to find the expectation value of the spin in the $y$ direction after applying a $\pi/2$-$\pi/2$ sequence of pulses. In Slichter's Principles of Magnetic Resonance, he does a $\pi/2$-$\pi$ ...