Since the National Institute of Standards and Technology (NIST) built its first superconducting devices for counting photons (the smallest units of light) in the 1990s, these once-rare detectors have become popular research tools all over the world. Now, NIST has taken a step toward enabling universal standards for these devices, which are becoming increasingly important in science and industry.
Click here for original story, Counting photons is now routine enough to need standards
Source: Phys.org