Abstract: Systems and methods for enhancing accuracy of electron pair approximation using non-bosonic perturbation (PT2) correction are provided. The method may comprise generating a unitary pair coupled cluster double (upCCD) Ansatz to determine geometry coordinates of a molecule, inputting, using a graphical user interface, the geometry coordinates of the molecule, performing, using a processor of a computing device comprising the processor and a memory, orbital optimization to generate an orbital optimization upCCD (oo-upCCD) comprising an energy calculation, and performing, using the processor, energy correction on the energy calculation of the oo-upCCD based on a second order perturbation theory (PT2), generating a PT2 correction energy value of the molecule. The computing device may comprise a quantum computer.