Detection of Macroscopic Entanglement by Correlation of Local   Observables
  We propose a correlation of local observables on many sites in macroscopic quantum systems. By measuring the correlation one can detect, if any, superposition of macroscopically distinct states, which we call macroscopic entanglement, in arbitrary quantum states that are (effectively) homogeneous. Using this property, we also propose an index of macroscopic entanglement. 
Akira Shimizu, Tomoyuki Morimae (Department of Basic Science,   University of Tokyo)