Research On Quantum Illumination Technology Based On Continuous Variable Entangled Light Source

Classical lidar is based on coherent state laser to detect target objects.It can obtain information of target objects by analyzing echo signals.It has important and wide application value in object imaging,environmental monitoring,target detection and other aspects.However,the traditional classical lidar detection system still has technical bottlenecks in anti-stealth,anti-clutter,anti-interference and so on.In view of the need to achieve more accurate radar detection and environment perception in complex scenarios,it is still necessary to explore a new radar detection mechanism based on new principles.Quantum entanglement technology provides a new research direction for quantum lidar detection.Quantum radar can introduce quantum technology into the transmitting or receiving end of radar,providing a new technical approach to improve the detection accuracy of traditional Lidar.With its unique quantum technology advantages,it has the potential to break through the detection function of traditional radar and improve the detection signal-to-noise ratio,which has become one of the main development directions for the detection of extremely weak target signals with higher accuracy.Among quantum radars,quantum illumination radar has become one of the hot spots in the new radar detection research at home and abroad because of its strong anti-jamming ability and the ability to realize remote weak signal detection.The quantum squeezed state and entangled state light field are important quantum resources because one component can break the standard quantum limit.Two single-mode squeezed states can be used to produce an entangled light field.The two modes of the entangled light field have quadrature amplitude correlation and quadrature bit correlation,which can be applied to quantum illumination radar.This thesis mainly studies quantum lighting technology based on the continuous variable entangled light source,and its main innovations are as follows:1.In the OPO(Optical parametric oscillator),the frequency disharmony between the fundamental and double frequency light due to different dispersion relationships in the nonlinear crystal is analyzed.An experimental system is built to test and analyze theoretically.We demonstrate the mechanism of double resonance enhanced squeezing state in OPO theoretically and experimentally.Three double resonance temperature points in the phase matching bandwidth of PPKTP(periodically poled potassium titanyl phosphate)crystal are measured directly and the corresponding squeezing levels are measured respectively.It was shown that squeezing of 11.7 d B,12.3 d B and 11.5 d B could be directly observed at three double resonance temperature points of 30.74℃,42.54℃ and53.71℃.Through the squeezing formula and the theoretical analysis of the overlap degree of the formants of the two beams at the double resonance temperature,it is confirmed that the difference in the squeezing level is due to the frequency detuning caused by the temperature-dependent dispersion.Therefore,the frequency detuning related to dispersion should be carefully calibrated in the experiment to improve the squeezing level of the double-resonance OPO.2.The differences between quantum lidar and classical Lidar and the basic principles of quantum illuminated radar are described briefly.A detection scheme of quantum illuminated radar based on a continuously variable entangled light source is proposed,and the feasibility of a detection sensitivity scheme oquantum-enhanceded optical receiver based on continuously variable entangled light field is verified through experimental studies.