I revisit the orignal proof of Bell’s theorem and give a thorough discussion about the assumptions that have been made. This shows that Bell’s inequality is violated in general not only by quantum systems but also by simple cassical systems with correlation. To get a grasp on that topic I will start with the general notion of entanglement.

Entanglement isn’t about interaction or information transfer betweeen entangled particles.

Consider spin-entaglement of two spin-$\frac{1}{2}$ particles.

Let them be in a singulet state relative to an arbitrary axis (say z-axis):

$$ |\Psi \rangle = \frac{1}{\sqrt{2}} (\ |\uparrow_z, \downarrow_z \rangle – |\downarrow_z,\uparrow_z\rangle \ ) $$ Continue reading “Bell’s theorem is wrong.”