Towards simulating molecular excited states on quantum computers

Simulation of molecular electronically excited states presents a unique opportunity for quantum computers. Excited states are often strongly correlated making accurate calculations from sophisticated quantum chemistry methods challenging even for relatively small molecules. Since it is expected that quantum computers will be most useful for solving strongly correlated problems, molecular excited state processes may be one of the first problems to take advantage of the quantum computing era. In this talk, I will outline several methods developed for computing excited states on a quantum computer. I will then present our team’s development of the quantum self-consistent equation-of-motion (q-sc-EOM) method and some of the new advances we are making in its implementation for small molecules. q-sc-EOM energies satisfy important relationships corresponding to the “killer condition” and “size-intensivity/extensivity” and, at the same time, q-sc-EOM is more robust to noise compared with current state-of-the-art methods.