Detecting mid-infrared light, one photon at a time

For some 30 years, scientists have used superconducting materials to record the tiniest specks of light imaginable—individual photons, or single particles of light. However, these detectors, which consist of ultracold wires only about one-thousandth the diameter of a human hair, were limited to recording single photons at visible-light and slightly longer wavelengths, in the near infrared (IR).