Heralding Single Photons Without Spectral Factorability

TL;DR

This paper demonstrates that high-purity heralded single photons can be generated without spectral factorability by using single-mode detection, challenging previous assumptions about the necessity of spectral factorability for high-quality photon sources.

Contribution

The study shows that spectral factorability is not required for high-purity heralded single photons, enabling simpler generation methods with non-factorable states using single-mode detection.

Findings

Single-mode detection achieves high purity with non-factorable states.

Spectral factorability is not essential for high-quality heralded photons.

Broadband filtering combined with single-mode measurement suffices.

Abstract

Recent efforts to produce single photons via heralding have relied on creating spectrally factorable two-photon states in order to achieve both high purity and high production rate. Through a careful multimode analysis, we find, however, that spectral factorability is not necessary. Utilizing single-mode detection, a similar or better performance can be achieved with non-factorable states. This conclusion rides on the fact that even when using a broadband filter, a single-mode measurement can still be realized, as long as the coherence time of the triggering photons exceeds the measurement window of the on/off detector.