  The categorization of quantum states for composite systems as either
separable or entangled, or alternatively as Bell local or Bell non-local states
based on local hidden variable theory is reviewed in Sections 1 and 2, focusing
on simple bipartite systems. The significance of states demonstrating Bell
non-locality for settling the long standing controversy between the Copenhagen
interpretation of the quantum measurement process involving the collapse of the
wave-function and the alternative interpretation based on pre-existing hidden
variables is emphasized. Although experiments demonstrating violations of Bell
locality in microscopic systems have now been carried out (see Section 3),
there is current interest in finding Bell non-locality in quantum systems on a
macroscopic scale, since this is a regime where a classical hidden variable
theory might still apply. Progress towards finding macroscopic quantum states
that violate Bell inequalities is reviewed in Section 4.
  A new test for Bell non-locality that applies when the sub-system measured
quantities are spin components with large outcomes is described, and applied to
four mode systems of identical massive bosons in Bose-Einstein condensates.
