title: Nonclassicality of quantum states: a hierarchy of observable conditions.
abstract: A necessary and sufficient hierarchy of conditions is derived that is completely equivalent to the failure of the Glauber-Sudarshan P function to be a probability density. The conditions are formulated in terms of experimentally accessible characteristic functions of quadratures.
authors.affiliation: Arbeitsgruppe Quantenoptik, Fachbereich Physik, Universität Rostock, D-18051 Rostock, Germany.
authors.forename: Th
authors.initials: T
authors.lastname: Richter
authors.forename: W
authors.initials: W
authors.lastname: Vogel