  Quantum computers have emerged as a promising platform to simulate the strong
electron correlation that is crucial to catalysis and photochemistry. However,
owing to the choice of a trial wave function employed in the popular hybrid
quantum-classical variational quantum eigensolver (VQE) algorithm, the accurate
simulation is restricted to certain classes of correlated phenomena. Herein, we
combine the spin-flip (SF) formalism with the unitary coupled cluster with
singles and doubles (UCCSD) method via the quantum equation-of-motion (qEOM)
approach to allow for an efficient simulation of a large family of strongly
correlated problems. In particular, we show that the developed
qEOM-SF-UCCSD/VQE method outperforms its UCCSD/VQE counterpart for simulation
of the cis-trans isomerization of ethylene and the automerization of
cyclobutadiene. The predicted qEOM-SF-UCCSD/VQE barrier heights for these two
problems are in a good agreement with the experimentally determined values. The
methodological developments presented herein will further stimulate
investigation of this approach for the simulation of other types of
correlated/entangled phenomena on a quantum computer.
