The Qu-candela project is an international project funded by the European commission (FP7) under the iMERA programme (implementing metrology in the European Research Area).
This project aims to address one of the Grand challenges on fundamental metrology of EMRP2007, namely the reformulation of the SI base unit the candela in terms of photon number (EMRP 2007, III.2.1, bullet 5, p. 26/47). The project forms the backbone of the EMRP roadmap Towards quantum photon-based standards for optical radiation.
The project was put together in answer to the call of the International Committee for Weights and Measures whether the candela definition could be reformulated in terms of photon number rather than in optical power. In this respect, that reformulation through linkage to Planck's constant, h, will provide greater consistency among the definitions of the base units and better serve the additional needs of emerging sectors such as the quantum based technologies as well as supporting classical radiometry.
This project brings together seven European national metrology institutes pooling resources from both the classical radiometry and single photon research to bridge the gap between macroscopic quantities like optical power and the photon counting in quantum world.