| In recent years,with the rapid development of science and technology,quantum science and information technology has become one of the frontiers research fields.Quantum clock synchronization technology is based on quantum light source and high-sensitivity quantum detection technology,which can greatly improve the accuracy of clock synchronization and has broad application prospects.Because the frequency entanglement source has strong frequency correlation and time correlation characteristics,it is usually used as the time signal carrier for quantum clock synchronization technology,and the characteristics of the frequency entanglement source will affect the clock synchronization accuracy.It will be beneficial to the application of quantum information technology through the study of the relevant quantum properties of frequency entangled sources.In addition,the frequency-entangled photons located in the communication band are very suitable for combining with optical fiber systems for the field of optical fiber quantum clock synchronization.This paper mainly focuses on the optimization of frequency entangled light sources in small communication bands and the rapid measurement of frequency entanglement characteristics.(1)The original miniaturized communication band frequency entanglement source in the laboratory has the problems of large volume and heavy weight,and because part of the optical path adopts free-space optical circuit devices,the entanglement source has poor stability and large transmission loss,which is difficult to meet the quantum requirements.The practical requirements of clock synchronization for highly reliable and miniaturized entanglement sources.By replacing all the spatial optical paths of the original entanglement source with the fiber coupling method,the frequency entanglement source in the all-fiber communication band is realized.Compared with the original entanglement source,the fiber-fiber coupling method has higher optical transmission efficiency,which is twice that of the free space-fiber coupling case.The overall optical power fluctuation of the entangled source is reduced from 7.6%to 1.0%.Under the pump light power of 10u W,the effective coincidence-to-accidental ratio(CAR)of the generated entangled photons was 10~4,and the HOM interference visibility reached 93.6%,which was the same as that of the entangled source before optimization.Quantum property measurements agree.The structure design of the entanglement source is further optimized.The original optical path system and the two independent chassis of the control circuit are combined into one chassis,The size of the whole machine is 37cm*16cm*21cm,and its weight is reduced by 50%,which has better portability.The entire entanglement source is more convenient and stable,and will better serve the subsequent field quantum clock synchronization experiments.(2)In order to realize the rapid measurement of the entanglement characteristics of the frequency entangled light source,a fast measurement method based on the frequency correlation coefficient r of the dual-channel filter and the dispersive element is proposed.The entangled two-photon source was verified experimentally.The r value is-0.996±0.008 from the measurement of the frequency anti-correlated entangled source;the r value of the frequency correlation entangled source is 0.991±0.152.The measurement results of this scheme are in good agreement with the results based on the joint spectrum measurement method,and it is expected to increase the measurement time to the second level.Due to the convenience and effectiveness of this method,it provides an alternative tool for rapid quantification of the frequency-dependent properties of entangled photon pairs. |
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