Collective multipole-like signatures of entanglement in symmetric   N-qubit systems
  A cogent theory of collective multipole-like quantum correlations in symmetric multiqubit states is presented by employing SO(3) irreducible spherical tensor representation. An arbitrary bipartite division of this system leads to a family of inequalities to detect entanglement involving averages of these tensors expressed in terms of the total system angular momentum operator. Implications of this theory to the quantum nature of multipole-like correlations of all orders in the Dicke states are deduced. A selected set of examples illustrate these collective tests. Such tests detect entanglement in macroscopic atomic ensembles, where individual atoms are not accessible. 
A. R. Usha Devi (1), R. Prabhu (1), (Department of Physics, Bangalore   University.), A. K. Rajagopal (2) (Department of Com...