# How does one produce entanglement?

In practice, when entangling two particles (say two electrons), is creating an entangled state purely a matter of bringing them close enough together? What I mean is, to make their wave functions correlated, is it just a matter of bringing them close enough together (regardless of what is required to accomplish this), or are there other processes necessary to cause the entanglement?

There is very good example about two entangled particles, for example We are in Lab, and we have a particle which has spin 0 ($S=0$) and that particle decays, and produces two electrons, and we have two sensors which measures spin of each electron, but according to Spin conservation sum of that electron's spins must be zero: $$S_{electron 1}+S_{electron 2}=0\tag{1.1}$$ And for example if first sensor (detector) measures that 1st electron's spin is $\uparrow$ then second electron's spin must be $\downarrow$ because $\uparrow +\downarrow=0$ which satisfies spin conservation equation. Heres a good animation of that event: Before measuring, state of electrons can be described using this equation: $$|\psi\rangle = \frac{|\uparrow\downarrow\rangle + |\downarrow\uparrow\rangle}{\sqrt{2}}\tag{1.2}$$ (in equation 1.2 there is same probability for finding electrons in state $|\uparrow\downarrow\rangle$ and $|\downarrow\uparrow\rangle$ but after measuring wavefunction 'collapses' to either $|\uparrow\downarrow\rangle$ or $|\downarrow\uparrow\rangle$)