# A Molecule-Based Single-Photon Source Applied in Quantum Radiometry

## TL;DR

This paper presents a traceably calibrated, molecule-based single-photon source with adjustable photon flux, high purity, and narrow bandwidth, suitable for quantum radiometry and calibration of photon detectors.

## Contribution

It introduces a novel organic dye molecule-based single-photon source with traceable flux control and high purity, advancing quantum radiometry standards.

## Key findings

- Photon flux adjustable between 144,000 and 1,320,000 photons/sec
- Second-order autocorrelation below 0.1 confirms high single-photon purity
- Effective calibration of silicon SPAD detector using the source

## Abstract

Single photon sources (SPSs) based on quantum emitters hold promise in quantum radiometry as metrology standard for photon fluxes at the low light level. Ideally this requires control over the photon flux in a wide dynamic range, sub-Poissonian photon statistics and narrow-band emission spectrum. In this work, a monochromatic single-photon source based on an organic dye molecule is presented, whose photon flux is traceably measured to be adjustable between 144 000 and 1320 000 photons per second at a wavelength of (785.6 +/- 0.1) nm, corresponding to an optical radiant flux between 36.5 fW and 334 fW. The high purity of the single-photon stream is verified, with a second-order autocorrelation function at zero time delay below 0.1 throughout the whole range. Featuring an appropriate combination of emission properties, the molecular SPS shows here application in the calibration of a silicon Single-Photon Avalanche Detector (SPAD) against a low-noise analog silicon photodiode traceable to the primary standard for optical radiant flux (i.e. the cryogenic radiometer). Due to the narrow bandwidth of the source, corrections to the SPAD detection efficiency arising from the spectral power distribution are negligible. With this major advantage, the developed device may finally realize a low-photon-flux standard source for quantum radiometry.

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Source: https://tomesphere.com/paper/1908.00616