Superconducting nanowire single-photon detectors (SNSPDs) now set the gold standard for low noise, high speed single-photon detection at telecom wavelengths, and are prized as single pixel detectors for a range of applications. The challenge is now open to optimise and benchmark these detectors for mid infrared wavelengths and to scale up to large area arrays, consolidating UK capability in this strategic emerging field. SNSPD’s will have their niche in high value applications, such as metrology, healthcare and other laboratory environments. WP3 is led by Robert Hadfield and will feed into WPs 4 and 6.