Sources emitting single photons are one of the key elements in emerging quantum optical technologies. During the development phase of devices for, say, radiometry with single photons, a fair comparison between the various stages requires common standards — a necessity that becomes even more important when the device is rolled out for mass production. But so far, there are no universal means to characterize single-photon sources.
Ekaterina Moreva and colleagues from the National Metrology Institutes of Italy, Germany and the UK have now joined forces to develop the first standardized technique to characterize single-photon sources and to provide common uncertainty estimation procedures. Using a Hanbury Brown and Twiss interferometer, the authors measured the coincidence and click probabilities from single photons emitted from a nitrogen–vacancy centre in diamond, allowing them to estimate the second-order correlation function — a parameter commonly used to describe single-photon sources. The independent results agree within uncertainty and mark the first step towards an international measurement standard for single-photon sources.
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Reichert, S. Common ground. Nature Phys 15, 110 (2019). https://doi.org/10.1038/s41567-019-0432-9
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DOI: https://doi.org/10.1038/s41567-019-0432-9