SIQUST project (2018-2021)
The aim of this project was to develop new absolute standard radiation sources, which exploit the discrete and quantum nature of photons. These sources are based on single-photon emitters with calculable photon emission rate and high purity, i.e. very low multiple photon emission probability. Such sources hold promise as new quantum standards with large numbers of applications, e.g. calibration of single-photon detectors, realization of the SI base unit candela, quantum random-number generation, quantum key distribution, sub-shot noise metrology, quantum-enhanced metrology, and photon-based quantum computation.
In this project, Metrology Research Institute (MRI) utilized the previously developed room temperature Predictable Quantum Efficient Detector (RT-PQED) to measure the single-photon flux produced by a single-photon source (SPS), which would use an optical excitation scheme (similar to the one developed in the project SIQUTE) developed by VTT-MIKES. The RT-PQED was used to calibrate a novel six-element cooled silicon detector (6X) manufactured by Metrosert for purposes of this project. The responsivity of the detector 6X was calibrated against PQED at the laser wavelengths of 647 nm and 676 nm by using 1-mm diameter of the laser beam (See the figure below) at MRI.
During the project MRI constructed a liquid nitrogen cooled cryostat for the PQED and characterize the effect of cooling on the PQED’s dynamic range. We verified the suitability of the PQED for calibrating the single photon detectors at a photon rate of 7 000 000 photons per second at a wavelength of 488.12 nm with a measurement uncertainty of below 0.15 % . We confronted with technical difficulties such as stability of the responsivity of the cooled PQED at one million photons per second at a wavelength of 930 nm. Work is ongoing to resolve such issues in the new EMPIR project SEQUME https://www.aalto.fi/en/department-of-signal-processing-and-acoustics/sequme-2021-2024
Contact persons: Farshid Manoocheri and Mikhail Korpusenko
Project website address: https://www.siqust.eu/
 F. Manoocheri et al, J. Phys. Conf . Ser 972, 012021 (2018)
 S. Porrasmaa et al , Opt Rev (2020), https://doi.org/10.1007/s10043-020-00580-1.