Symmetry-Adapted Encoding for Reducing the Qubit Requirement of Electronic Structure Theory on Quantum Annealers

Quantum chemistry is one of the most promising applications of quantum computation due to the potential of major speedup of computing time. Here, we combine a symmetry-adapted Jordan-Wigner encoding with the Xia-Bian-Kais (XBK) method to reduce the qubit requirement and improve the efficiency of electronic structure theory calculations on quantum annealers. We demonstrate the effectiveness of this method by calculating the potential energy surface of a set of small molecules, including ones larger than those that have been reported from simulating with a quantum algorithm. We have also identified cases where results from the XBK method with symmetry-adapted encodings would deviate from the non-symmetry-adapted results, and we provide an explanation.