MODE ENTANGLEMENT IN NONDEGENERATE DOWN-CONVERSION WITH QUANTIZED PUMP

We study entanglement between field modes in the process of nondegener ate two-photon down-conversion with quantized pump. We show that due t o the quantum nature of the dynamics, strong entanglement between the pump and the signal-idler subsystems can be observed. We find that the higher the initial intensity of the pump mode the stronger the entang lement between the pump and the signal-idler subsystem is established during the first instants of the time evolution. We also show that the signal and the idler modes are strongly entangled (correlated). This entanglement is much stronger than the entanglement between the pump a nd the signal-idler subsystem. Correlation between the signal and the idler modes leads to a high degree of two-mode squeezing, which can be observed during the first instants of the time evolution when the pum p mode is still approximately in a pure state. On the other hand, the back action of the signal-idler subsystem on the pump mode leads to a strong single-mode squeezing of the pump mode. At the time interval du ring which squeezing of the pump mode can be observed the pump mode is far from being in the minimum uncertainty state. We also analyze the longtime behavior of the quantum-optical system under consideration an d we show that the interesting collapse-revival effect in the time evo lution of the mean photon number and of the purity parameters of field modes can be observed. Finally, we show that the degree of entangleme nt between modes in the nondegenerate quantum-optical down-conversion strongly depends on the initial state of the system.