The open-source python package QuantumSymmetry: the water molecule on four qubits

The symmetry-adapted encodings (SAEs) provide a useful tool to reduce the computational requirements of the simulation of molecular systems on quantum computers. This is achieved by harnessing the physical symmetries of the molecular system under consideration. They can also enable qubit-based complete active space approximation. The present work explores aspects of the symmetry-adapted encoding in the form of an opensource Python software, QuantumSymmetry, by considering a simple example of molecular system, that of the water molecule.