Nonclassicality filters and quasiprobabilities

Understand

Necessary and sufficient conditions for the nonclassicality of bosonic quantum states are formulated by introducing nonclassicality filters and nonclassicality quasiprobability distributions.

• Regular quasiprobabilities are constructed from characteristic functions which can be directly sampled by balanced homodyne detection.
• Their negativities uncover the nonclassical effects of general quantum states.
• The method is illustrated by visualizing the nonclassical nature of a squeezed state.