  We witness experimentally the presence of macroscopic coherence in Gaussian
quantum states using a recently proposed criterion (E.G. Cavalcanti and M.
Reid, Phys. Rev. Lett. 97, 170405 (2006)). The macroscopic coherence stems from
interference between macroscopically distinct states in phase space and we
prove experimentally that even the vacuum state contains these features with a
distance in phase space of $0.51\pm0.02$ shot noise units (SNU). For squeezed
states we found macroscopic superpositions with a distance of up to
$0.83\pm0.02$ SNU. The proof of macroscopic quantum coherence was investigated
with respect to squeezing and purity of the states.
