  Two nonlinear Kerr oscillators mutually coupled by parametric pumping are
studied as a source of states entangled in photon numbers. Temporal evolution
of entanglement quantified by negativity shows the effects of sudden death and
birth of entanglement. Entanglement is preserved even in asymptotic states
under certain conditions. The role of reservoirs at finite temperature in
entanglement evolution is elucidated. Relation between generation of entangled
states and violation of Cauchy-Schwartz inequality for oscillator intensities
is found.
