CHARACTERIZATIONS OF CLASSICAL AND NONCLASSICAL STATES OF QUANTIZED RADIATION

A new operator-based condition for distinguishing classical from noncl assical states of quantized radiation is developed. It exploits the fa ct that the normal ordering rule of correspondence to go from classica l to quantum-dynamical variables does not in general maintain positivi ty. It is shown that the approach naturally leads to distinguishing se veral layers of increasing nonclassicality, with more layers as the nu mber of modes increases. A generalization of the notion of sub-Poisson ian statistics for two-mode radiation fields is achieved by analysing completely all correlations and fluctuations in quadratic combinations of mode annihilation and creation operators conserving the total phot on number. This generalization is nontrivial and intrinsically two-mod e as it goes beyond all possible single mode projections of the two-mo de field. The nonclassicality of pair-coherent states, squeezed vacuum and squeezed thermal states is analysed and contrasted to one another , comparing the generalized sub-Poissonian statistics with extant sign atures of nonclassical behaviour.