Numerical modeling of the multi-stage Stern$\unicode{x2013}$Gerlach experiment by Frisch and Segr\`e using co-quantum dynamics via the Bloch equation

We numerically study the spin flip in the Frisch$\unicode{x2013}$Segr\`e experiment, the first multi-stage Stern$\unicode{x2013}$Gerlach experiment, within the context of the novel co-quantum dynamics theory. We model the middle stage responsible for spin rotation by sampling the atoms with the Monte Carlo method and solving the dynamics of the electron and nuclear magnetic moments numerically according to the Bloch equation. Our results show that, without using any fitting parameters, the co-quantum dynamics closely reproduces the experimental observation reported by Frisch and Segr\`e in 1933, which has so far lacked theoretical predictions.