2 - Two Faces of Quantum Nonlocality and Two Interpretations of Quantum State

Summary

This chapter is a step towards understanding why quantum nonlocalityis a misleading concept. Metaphorically speaking, quantum nonlocality isJanus faced. One face is an apparent nonlocality of the state update basedon the Luders projection postulate. It can be referred as intrinsic quantumnonlocality. And the other face is subquantumnonlocality: by introducing a special model with hidden variables onederives the Bell inequality and claims that its violation implies the existenceof mysterious instantaneous influences between distant physical systems(Bell nonlocality). According to the Luders projection postulate, aquantum measurement performed on one of the two distant entangled physicalsystems, say on S1, modifies instantaneously the state of S2. Therefore, ifthe quantum state is considered to be an attribute of the individual physicalsystem (Copenhagen interpretation) and if one assumes thatexperimental outcomes are produced in a random way one arrives at the contradiction. It is a primary source of speculation about aspooky action at the distance. But Einstein had already pointed out that the quantum paradoxes disappear, ifone adopts the statistical interpretation.