Superposition of macroscopically distinct states means large multipartite entanglement

I show relations between superposition of macroscopically distinct states and entanglement. These relations lead to the important conclusion that if a state includes superposition of macroscopically distinct states, the state also includes large multipartite entanglement in terms of several measures. Such a multipartite entanglement property also suggests that if a state includes superposition of macroscopically distinct states, a measurement on a single particle drastically changes the state of macroscopically many other particles, as in the case of the N-qubit Greenberger- Horne-Zeilinger state. ©2010 The American Physical Society