C. Brif et al., GENERALIZED COHERENT STATES ARE UNIQUE BELL STATES OF QUANTUM-SYSTEMSWITH LIE-GROUP SYMMETRIES, Physical review. A, 57(2), 1998, pp. 742-745
We consider quantum systems, whose dynamical symmetry groups are semis
imple Lie groups, which can be split or decay into two subsystems of t
he same symmetry. We prove that the only states of such a system that
factorize upon splitting are the generalized coherent states. Since Be
ll's inequality is never violated by the direct product state. when th
e system prepared in the generalized coherent state is split, no quant
um correlations are created. Therefore the generalized coherent states
are the unique Bell states, i.e., the pure quantum states preserving
the fundamental classical property of satisfying Bell's inequality upo
n splitting.