Nonclassicality of two-mode states of the quantized radiation field

摘要

The second-order coherence (correlation) functions are used to investigate the classicality (nonclassicalily) of quantum states, as defined by the existence (nonexistence) of a positive definite (Glauber-Sudarshan) P-representation. We study nonclassical behavior as revealed by sub-Poissonian statistics and/or violation of the classical Cauchy-Schwarz inequality. The two-mode states considered include Bell-like superpositions of Fock states, Schroedinger cat states and the ideal squeezed states.