| The use of objective physical effects instead of physical standard devices is one of the development trends of metrology standards.Its main method is to reduce the cumulative error introduced and improving the reproducibility and accuracy of the benchmark by the physical standard instrument.Change from the traditional traceable optical radiation calibration method to the field of quantum measurement,it is necessary to realize high-precision measurement of photon number and establish an absolute radiation reference from optical power P measurement to photon count value N measurement.To realize this process,two problems need to be solved:establishing standard single photon detectors for transmission and preparing standard single photon sources for on-demand emission.Accurate measurement of the absolute quantum efficiency of a single photon detector is a prerequisite for establish standard transfer single photon detectors.Based on the theory of the parametric down-conversion time interval method,this paper innovatively proposes a quantum efficiency correction model by analyzing the effects of dead time,afterpulse,coincidence loss,loss factor,double channel bandwidth matching and other factors on double channel coincidence counting.According to the calibration principle,a quantum efficiency measuring device for standard single photon detectors is established.The nonlinear BBO crystal is pumped by 355nm laser source generated by continuous power tunable laser,and the correlated photons with 603nm and 863nmnm wavelengths are prepared The coupling optimization of pump light and crystal,the spatial location of signal light and idle light,and the research of background radiation suppression technology are carried out.Combining spectral separation and spatial separation,the design of background light suppression optical path with combined cutoff depth OD?11 is realized,and the influence of residual pump light on photon count value and coincidence measurement is reduced.Finally,the signal-to-noise ratio is better than 45:1,the calibration results with correlation photon number rate better than 107/s,the minimum deviation of quantum efficiency is 0.17%and detector quantum efficiency calibration accuracy better than 1.23%are achieved.In this paper,a predictive single photon source device is established.In the experiment,by adding a beam splitter in one direction of the relevant photons,based on the random selection characteristic of single photon paths and combined with anti-coincidence measurement technology,the measurement results of single photon source multi-photon probability less than 7×10-5 are obtained,the influence of multi-photon event on single photon source is effectively reduced,and the quasi-single photon source with better single photon property is obtained.The output photons based on the predictive single photon source are difficult to obey the Uniform distribution characteristics in the time series and cannot meet the use requirements of the single photon source.The fabrication scheme of cavity storage single photon source is further considered in this paper.This scheme uses the natural advantage of non-collinear phase-matching two-photon space separation of parametric down conversion to store photons in one output direction and detect the other.It is proposed to realize a large dynamic range of single light source output by changing the single photon storage time and tuning the single photon time interval for dynamic output.The photon source scheme based on parametric down-conversion method can solve the problem of limited radiation calibration accuracy of traditional laser attenuation method,and reflects the development trend of future calibration methods towards absolute and on-site measurement.The development of this new radiation calibration technology will play an important role in the future space radiation reference source and high-precision satellite radiation calibration,quantum communication and low-light level fields,environmental monitoring and climate research programs. |
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