Characterizing heralded single-photon sources with imperfect measurement devices

TL;DR

This paper develops a theoretical framework and experimental validation for accurately characterizing heralded single-photon sources using imperfect measurement devices, addressing limitations of detectors and measurement methods.

Contribution

It introduces a method to infer true source properties from time-averaged measurements considering detector imperfections and source limitations.

Findings

Theoretical model accurately predicts source coherence from imperfect data.

Experimental demonstration confirms the model's effectiveness with a PPKTP crystal.

Achieved a single-photon generation rate of 1.2 million per second per milliwatt.

Abstract

Any characterization of a single-photon source is not complete without specifying its second-order degree of coherence, i.e., its $g^{(2)}$ function. An accurate measurement of such coherence functions commonly requires high-precision single-photon detectors, in whose absence, only time-averaged measurements are possible. It is not clear, however, how the resulting time-averaged quantities can be used to properly characterize the source. In this paper, we investigate this issue for a heralded source of single photons that relies on continuous-wave parametric down-conversion. By accounting for major shortcomings of the source and the detectors--i.e., the multiple-photon emissions of the source, the time resolution of photodetectors, and our chosen width of coincidence window--our theory enables us to infer the true source properties from imperfect measurements. Our theoretical results are corroborated by an experimental demonstration using a PPKTP crystal pumped by a blue laser, that results in a single-photon generation rate about 1.2 millions per second per milliwatt of pump power. This work takes an important step toward the standardization of such heralded single-photon sources.