A two-loop provider (or two-loop program) is a specialised software for generating two-loop amplitudes for perturbative quantum field theory calculations. They are a special case of external amplitude providers. Two-loop amplitudes contribute to NNLO (and higher order) cross sections as well as the NLO cross sections of loop-induced processes.
List of two-loop providers
- S. P. Jones, Automation of 2-loop Amplitude Calculations, PoS LL2016 (2016) 069, arXiv:1608.03846