An international team of scientists, including Silvie Illésová from IT4Innovations, has introduced a new quantum algorithm – SA-OO-VQE – in the prestigious Journal of Chemical Theory and Computation. The algorithm significantly facilitates the simulation of molecules involving multiple electronic states simultaneously. Only part of the algorithm is executed on quantum processors, while the remainder runs on classical computers. Some of the computations were carried out on IT4Innovations’ supercomputers.

SA-OO-VQE enables a more accurate description of key phenomena such as conical intersections – scenarios where ground and excited states become degenerate, i.e. have the same energy. These processes are fundamental to photochemical reactions and many other biological and materials-related processes.

The algorithm has been specifically designed to run on today’s quantum computers, at the beginning of the NISQ era, which are limited in the number of qubits and are highly susceptible to quantum noise that hinders precise calculations. “Computational tasks are therefore split between quantum and classical architectures, which helps effectively overcome technical limitations,” explains Silvie Illésová.

Martin Beseda from the University of L’Aquila (formerly IT4Innovations) adds: “This new version of SA-OO-VQE is capable of naturally operating with a quasi-diabatic representation of orbitals. This approach significantly simplifies and accelerates the subsequent modelling of chemical reactions, as the results require minimal post-processing – saving both researchers’ time and computational resources.”

The algorithm was successfully tested on the formaldimine molecule, which exhibits a well-known conical intersection between its ground and first excited electronic states. “This test confirmed the practical applicability of our method,” says Silvie Illésová.

Thanks to this new approach, researchers can now more accurately simulate the motion of atoms in molecules undergoing complex changes involving multiple interacting electronic states. This advancement paves the way for the exploration of more complex molecules and scenarios – essential for the development of new materials, medicines, and energy storage technologies.

 

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