Analytic energy gradient for stateaveraged orbitaloptimized variational quantum eigensolvers and its application to a photochemical reaction
Abstract
Elucidating photochemical reactions is vital to understand various biochemical phenomena and develop functional materials such as artificial photosynthesis and organic solar cells, albeit its notorious difficulty by both experiments and theories. The best theoretical way so far to analyze photochemical reactions at the level of ab initio electronic structure is the stateaveraged multiconfigurational selfconsistent field (SAMCSCF) method. However, the exponential computational cost of classical computers with the increasing number of molecular orbitals hinders applications of SAMCSCF for large systems we are interested in. Utilizing quantum computers was recently proposed as a promising approach to overcome such computational cost, dubbed as SA orbitaloptimized variational quantum eigensolver (SAOOVQE). Here we extend a theory of SAOOVQE so that analytical gradients of energy can be evaluated by standard techniques that are feasible with nearterm quantum computers. The analytical gradients, known only for the statespecific OOVQE in previous studies, allow us to determine various characteristics of photochemical reactions such as the minimal energy (ME) points and the conical intersection (CI) points. We perform a proofofprinciple calculation of our methods by applying it to the photochemical {\it cistrans} isomerization of 1,3,3,3tetrafluoropropene. Numerical simulations of quantum circuits and measurements can correctly capture the photochemical reaction pathway of this model system, including the ME and CI points. Our results illustrate the possibility of leveraging quantum computers for studying photochemical reactions.
 Publication:

arXiv eprints
 Pub Date:
 July 2021
 arXiv:
 arXiv:2107.12705
 Bibcode:
 2021arXiv210712705A
 Keywords:

 Physics  Chemical Physics;
 Condensed Matter  Strongly Correlated Electrons;
 Quantum Physics
 EPrint:
 21 pages, 6 figures