On ideal class group computation of imaginary multiquadratic fields

In the paper, we extend Biasse — van Vredendaal (OBS, 2019, vol. 2) implementation and experiments of the class group computation from real to imaginary multiquadratic fields. The implementation is optimized by introducing an explicit prime ideal lift operation and by using LLL reduction instead of HNF computation. We provide examples of class group computation of the imaginary multiquadratic fields of degree 64 and 128, that has been previously unreachable.