We review radiometric techniques that take advantage of photon counting and stem from the quantum laws of nature. We present a brief history of metrological experiments and review the current state of experimental quantum radiometry.
Abstract Single-photon sources have a variety of applications. One of these is quantum radiometry, which is reported on in this paper in the form of an overview, specifically of the current state of the art in the application of deterministic single photon sources to the calibration of single photon detectors. To optimize single-photon sources for this purpose, extensive research is currently carried out at the European National Metrology Institutes (NMIs), in collaboration with partners from universities. Single-photon sources of different types are currently under investigation, including sources based on defect centres in (nano-)diamonds, on molecules and on semiconductor quantum dots. We will present, summarise, and compare the current results obtained at European NMIs for single-photon sources in terms of photon flux, single-photon purity, and spectral power distribution as well as the results of single-photon detector calibrations carried out with this type of light sources.
In this presentation a review about the current state of the art concerning the application of deterministic single photon sources for absolute radiometry, i.e. the calibration of single photon detectors, is given. At the Physikalisch-Technische Bundesanstalt, the German national Metrology institute, an extensive research is carried out to optimize single photon sources for this purpose. Different single photon sources are currently under investigation, these are sources based on defect centres in (nano-)diamonds, on molecules and on semiconductor quantum dots.
In this review article we summarize all experiments claiming quantum computational advantage to date. Our review highlights challenges, loopholes, and refutations appearing in subsequent work to provide a complete picture of the current statuses of these experiments. In addition, we also discuss theoretical computational advantage in example problems such as approximate optimization and recommendation systems. Finally, we review recent experiments in quantum error correction --- the biggest frontier to reach experimental quantum advantage in Shor's algorithm.