We introduce a quantitative measure of nonclassical behavior based on negative regions of quasiprobability distributions. Zeros of the antinormal ordered phase-space representation characterize a state to be maximally nonclassical with respect to this measure. All pure states of a particle or of a single field mode, except those with Gaussian quasiprobability distributions, have one or more zeros in this representation.

• Received 18 July 1994

DOI:https://doi.org/10.1103/PhysRevA.51.3340