Abstract
Heralded single photon sources are often implemented using spontaneous parametric downconversion, but their quality can be restricted by optical loss, double pair emission and detector dark counts. Here, we propose a scheme using cascaded downconversion that would improve the performance of such sources by providing a second trigger signal to herald the presence of a single photon, thereby reducing the effects of detector dark counts. Our calculations show that for a setup with fixed detectors, an improved heralded second-order correlation function g(2) can be achieved with cascaded downconversion given sufficient efficiency for the second downconversion, even for equal single-photon production rates. Furthermore, the minimal g(2) value is unchanged for a large range in pump beam intensity. These results are interesting for applications where achieving low, stable values of g(2) is of primary importance.
Highlights
Single photons constitute an important resource for several quantum optical applications, such as optical quantum computing, randomness generation or quantum communication [1]
A common way to implement heralded sources is through the process of spontaneous parametric downconversion (SPDC)
Given a fixed SPDC-based heralded single photon source and detectors, is it advantageous to pump it using heralded single photons rather than just using a coherent beam from a laser? We address these questions first using an analytic treatment in section II, followed by a more exact numerical simulation in section III based on the detector statistic model introduced by Bussieres et al.[26]
Summary
Single photons constitute an important resource for several quantum optical applications, such as optical quantum computing, randomness generation or quantum communication [1]. We investigate a different approach to improve the statistics of heralded single photons from SPDC, which is to use photon precertification [17], implemented with cascaded downconversion (CSPDC) as shown in Figure 1 (b). The main benefit is to provide a second heralding signal which can reduce the negative effects of dark counts at the heralding detectors. This approach can potentially result in single photons with a lower heralded second-order correlation function g(2)[22], given by g(2) = T1ABS1 ,.
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