I’m trying to implement Configuration interaction calculations in psi4 (using examples given in psi4numpy). The helper_CI.py has implementation of bit-determinants, this seems to be a very efficient way to implement Slater-Condon rules to calculate one- and two- electron operators in terms of determinants. I have been trying to find a reference for this form of implementation, and found this.

Does anyone here, know a reference for the implementation of bit-determinants for CI and slater-condon rules?