Abstract

To dintinguish between classical and non-classical states in quantum mechanics and quantum optics various authors use the criterion of positive-semidefiniteness and regularity of the s-quasiprobabilities W(α,s). Of main interest has been the Wigner function or the symmetrically ordered quasiprobability W(α,0). Hudson¹ has shown that of all the pure states, only the coherent and squeezed states satisfy the condition that the Wigner function is positive semidefinite.

© 1994 IEEE