The Influence Of Noise From Injected Fields Of Optical Parametric Oscillator On The Quantum Entanglement Characteristics Of Output Fields

The continuous variable entangled state is one of the important basic resources for studying quantum information.In order to improve the efficiency and quality of quantum information processing,researchers put forward higher requirements for the degree of entanglement of continuous variable entangled states.In the experiment,the non-degenerate optical parametric oscillator(NOPO)is commonly used to prepare the continuous variable entangled state with.In general,NOPO performs the nonlinear operation on the coherent state noise of injected pump field and signal(idle)field.However,there is no report about the manipulation of NOPO for other quantum state noise(phase squeezed states and EPR state).Therefore,we studied the effects of quantum noise of the injected pump field,injected signal field and idle field on the entanglement characteristic of NOPO output fields theoretically,so as to find ways to improve the entanglement characteristic of the NOPO output fields.The main works of this paper include the following contents.(1)We analyzed the NOPO system for preparing continuous variable entangled state,and optimized parameter for the performance of the system.Under the condition that the pump field is in the coherent state and that the injected signal(idle)field is in the vacuum state,we analyzed the effect of cavity detuning on the entanglement characteristic of the NOPO output fields.And the results showed that the smaller the cavity detuning was,the better the entanglement characteristic of the output fields were,and that when the cavity was resonance,the entanglement characteristic of the output fields were the best.Then,we analyzed the effect of other experimental system parameters on the entanglement characteristic of the output fields when the cavity was resonance,it could further reduce the influence of noise of NOPO injected fields on the entanglement characteristic of the output fields to select the pump parameters and the transmission coefficient of the pump field as small as possible and the transmission coefficient of the signal(idle)field aslarge as possible,thus improving the entanglement characteristic of the output fields.(2)On the basis of the optimization of system parameters,we studied the effect of quantum noise of different injected fields on the entanglement characteristic of the output fields.And it was found that it could further improve the entanglement characteristic of the NOPO output fields if we selected the phase-squeezed pump field,two-modes squeezed signal field and idle field as the injected signals,and that the higher the squeezing factors were,the better the entanglement characteristic was.The parameters selected in the above theoretical analysis fitted the previous NOPO experiments,and the results obtained can provide reference for the improvement of the entanglement characteristic of the output fields in the future experiments of preparing continuous variable entangled state light by NOPO.