October 27, 2017 The following three pilot comparisons were performed at INRIM, with the participation of CMI, NPL and PTB, from 16-27 October 2017 Detection efficiency: At 1550 nm, on a fibre-coupled free-running single-photon avalanche detector (idQuantique ID220). Glauber second-order auto-correlation function of a single-photon source: At 710 nm, on emission from a nitrogen vacancy centre in diamond; At 1550 nm, on emission from a heralded single-photon source.